Class 8: Chapter 22- Linear Equations Exercise 22B Q1. 17 less than four times a number is 11. Find the number. πΏππ‘ π‘βπ ππ’ππππ = π₯ 4π₯ β 17 = 11 28 π₯= =7 4 Q2. If 10 be added to four times a certain number, the result is 5 less than five times the number. Find the number πΏππ‘ π‘βπ ππ’ππππ=π₯ 4π₯ + 10 = 5π₯ β 5 π₯ = 15 Q3. 2 3 of a number is 20 less than the original number. Find the original number. πΏππ‘ π‘βπ ππππππππ ππ’ππππ = π₯ 2 π₯ = π₯ β 20 3 1 π₯ = 20 3 π₯ = 60 Q.4 A number is 25 more than its part. Find the number. πΏππ‘ π‘βπ ππ’ππππ = π₯ 5 π₯ = 25 + π₯ 6 1 π₯ = 25 6 π₯ = 150 Q.5 A number is as much greater than 21 as is less than 71. Find the number. πΏππ‘ π‘βπ ππ’ππππ = π₯ π₯ β 21 = 71 β π₯ 2π₯ = 92 π₯ = 46 Q.6 6 more than one-fourth of the number is two-fifth of the number. Find the number. πΏππ‘ π‘βπ ππ’ππππ = π₯ 1 2 π₯+6 = π₯ 4 5 2 1 30 6 = ( β )π₯ = π₯ 5 4 20 π₯ = 40 1 For more information please go to: https://icsemath.com/ Q.7 One-third of a number exceeds one-fourth of the number by 15 . Find the number. πΏππ‘ π‘βπ ππ’ππππ = π₯ 1 1 π₯ β π₯ = 15 3 4 1 π₯ = 15 ππ π₯ = 180 12 Q.8 If one-fifth of a number decreased by 5 is 16, find the number. πΏππ‘ π‘βπ ππ’ππππ = π₯ 1 π₯ β 5 = 16 5 π₯ = 105 Q.9 A number when divided by 6 is diminished by 40. Find the number. πΏππ‘ π‘βπ ππ’ππππ = π₯ π₯ = π₯ β 40 6 5 π₯ = 40 6 π₯ = 48 Q.10 Four-fifths of a number exceeds two-third of the number by 10. Find the number. πΏππ‘ π‘βπ ππ’ππππ = π₯ 4 2 π₯ = π₯ + 10 3 3 2 ππ π₯ = 10 15 ππ π₯ = 75 Q.11 Two numbers are in the ratio 3:4 and their sum is 84. Find the number πΏππ‘ π‘βπ π‘π€π ππ’πππππ ππ π₯ πππ π¦ Therefore 3π₯ = 4π¦ π₯ + π¦ = 84 Solving 4 π¦ + π¦ = 84 3 7π¦ = 84 3 π¦ = 3 × 12 = 36 4 π»ππππ, π₯ = × 36 = 48 3 Q.12 Three numbers are in ratio 4:5:6 and their sum is 135. Find the numbers. πΏππ‘ π‘βπ π‘βπππ ππ’πππππ ππ π₯, π¦, π§ Therefore, 4π₯: 5π₯: 6π₯ 2 For more information please go to: https://icsemath.com/ 4π₯ + 5π₯ + 6π₯ = 135 Solving, 15π₯ = 135 π₯=9 Therefore πβπ π‘βπππ ππ’πππππ πππ 36, 45, 54 Q.13 Two numbers are in the ratio 3:5. If each is increased by 10, then ratio between the new numbers so formed is 5:7, Find the original numbers. πΏππ‘ π‘βπ π‘π€π ππ’πππππ ππ π₯ πππ π¦ πΊππ£ππ, π₯ 3 = β¦ β¦ β¦ β¦ β¦ β¦ β¦ β¦ π) π¦ 5 π₯ + 10 5 = β¦ β¦ β¦ β¦ β¦ β¦ β¦ ππ) π¦ + 10 7 π πππ£πππ, 3 πΉπππ π) π₯ = π¦ 5 ππ’ππ π‘ππ‘π’π‘πππ ππ ππ) 3 π¦ + 10 5 5 = π¦ + 10 7 21 π¦ + 70 = 5π¦ + 50 5 4 20 = π¦ 5 ππ π¦ = 25 3 π₯ = × 25 = 15 5 ππ€π ππ’πππππ πππ 15 πππ 25 Q.14 The sum of three consecutive odd numbers is 75. Find the numbers. πΏππ‘ π‘βπ π‘βπππ ππππ πππ’π‘ππ£π ππ’πππππ ππ π₯, π₯ + 2, π₯ + 4 π‘βπππππππ, π₯ + π₯ + 2 + π₯ + 4 = 75 3π₯ + 6 = 75 3π₯ = 69 π₯ = 23 πβπππππππ π‘βπ π‘βπππ ππ’πππππ πππ 23, 25 πππ 27 Q.15 Divide 25 into two parts such that 7 times the first part added to 5 times the second part makes 139. Let π‘βπ π‘π€π ππππ‘π ππ π₯ πππ π¦ Therefore π₯ + π¦ = 25 7π₯ + 5π¦ + 139 Solving we get 3 For more information please go to: https://icsemath.com/ π₯ = 25 β π¦ 7(25 β π¦) + 5π¦ = 139 175 β 2π¦ = 139 2π¦ = 175 β 139 = 36 ππ π¦ = 18 πβπ ππ‘βππ ππππ‘ = 7 Q.16 Divide 180 into two parts such that the first part is 12 less than twice the second part. Let π‘βπ π‘π€π ππππ‘π ππ π₯ πππ 2π¦ Therefore π₯ + π¦ = 180 π₯ + 12 = 2π¦ Solving π¦ = 180 β π₯ π₯ + 12 = 2(180 β π₯) 3π₯ = 360 β 12 = 348 π₯ = 116 πβπππππππ π¦ = 180 β 116 = 64 Q.17 The denominator of the fraction is 4 more than its numerator. On subtracting 1 from each numerator and denominator the fraction becomes . Find the original fraction. π₯ Let the fraction be π¦ Given π¦ =π₯+4 π₯ πβππππππ π‘βπ πππππ‘πππ = π₯+4 Given, π₯β1 1 = π₯+4β1 2 2π₯ β 2 = π₯ + 3 π₯ = 5 πππ π¦ = 9 5 πβπππππππ πππππ‘πππ = 9 Q.18 The denominator of the fraction is 1 more than the double the numerator. On adding 2 to the numerator and subtracting 3 from denominator, we obtain 1. Find the original fraction. π₯ Let the fraction be 2π₯ + 1 Given π₯+2 =1 2π₯ + 1 β 3 π₯ + 2 = 2π₯ β 2 π₯=4 4 Fraction = 9 4 For more information please go to: https://icsemath.com/ Q.19 The sum of the digits of a two-digit number is 5. On adding 27 to the number, its digits are reversed. Find the original number. Let π‘βπ π‘π€π πππππ‘ ππ’ππππ ππ π₯π¦ πΊππ£ππ π₯ + π¦ = 5 β¦ β¦ β¦ β¦ β¦ β¦ β¦ . π) π₯π¦ + 27 = π¦π₯ 10π₯ + π¦ + 27 = 10π¦ + π₯ 9π₯ + 27 = 9π¦ ππ π₯ + 3 = π¦ β¦ β¦ β¦ β¦ β¦ β¦ β¦ ππ) ππππ£πππ π) πππ ππ) π‘ππππ‘βππ. π₯ + 3 = (5 β π₯ ) 2π₯ = 2 π₯=1 π¦=4 π»ππππ π‘βπ ππ’ππππ = 14 Q.20 What same numbers should be added to each one of the number 15,23,29,44 to obtain numbers which are in proportion? πΏππ‘ π‘βπ ππ’ππππ πππππ π‘π πππβ πππ ππ 15, 23, 29, 44 ππ π₯ 15 + π₯ 29 + π₯ = 23 + π₯ 44 + π₯ 660 + 59π₯ + π₯ 2 = 667 + 52π₯ + π₯ 2 7π₯ = 7 π₯=1 Q.21 The sum of two numbers is 110. One-fifth of the larger number is 8 more than oneninth of the smaller number. Find the numbers. πΏππ‘ π‘βπ π‘π€π ππ’πππππ ππ π₯ πππ π¦ Given π₯ + π¦ 110 1 1 π₯ = π¦+8 5 9 Solving 1 1 π₯ = (110 β π₯ ) + 8 5 9 1 1 110 182 ( + )π₯ = +8 = 5 9 9 9 182 × 45 π₯= = 65 9 × 14 π¦ = 10 β 65 = 45 ππ€π ππ’πππππ πππ 45 πππ 65 Q22 A number is subtracted from the numerator of the fraction 1 12 and six times that 13 number is added to the denominator. If the new fraction is then find the number. 11 πΏππ‘ π‘βπ ππ’ππππ π π’ππ‘ππππ‘ππ ππππ π‘βπ ππ’πππππ‘ππ = π₯ 5 For more information please go to: https://icsemath.com/ 12 β π₯ 1 = 13 + 6π₯ 11 132 β 11π₯ = 13 + 6π₯ 17π₯ = 119 ππ π₯ = 7 Q.23 A right angled triangle having perimeter 120cm has its two side perpendicular side in the ratio 5:12. Find the lengths of its sides. πππππππ‘ππ ππ πππβπ‘ ππππππ π‘πππππππ = 120 ππππππππππ’πππ π ππππ = 5π₯ πππ 12π₯ π»π¦πππ‘πππ’π π = β(5π₯)2 + (12π₯ )2 = 13π₯ Therefore 5π₯ + 12π₯ + 13π₯ = 120 30π₯ = 120 π₯=4 Therefore length of side = 20, 48, 52 Q.24 The sum of the digits of a two-digit number is 9. If 9 is added to the number formed by reversing the digits, then the result is thrice the original number. Find the original number. πΏππ‘ π‘βπ π‘π€π πππππ‘ ππ’ππππ = π₯π¦ π₯ + π¦ = 9 β¦ β¦ β¦ . . π) π¦π₯ + 9 = 3(π₯π¦) 10π¦ + π₯ + 9 = 3(10π₯ + π¦) 10π¦ + π₯ + 9 = 30π₯ + 3π¦ π¦ + 9 = 29π₯ β¦ β¦ β¦ β¦ ππ) ππππ£πππ π) πππ ππ) 7(9 β π₯ ) + 9 = 29π₯ 63 β 7π₯ + 9 = 29π₯ 72π₯ = 36 ππ π₯ = 2 π¦=9β2=7 πβπππππππ π‘βπ ππ’ππππ = 27 Q.25 The lengths of a rectangle plot of land exceeds its breadth by 23 m. if the length is decreased by 15 m. and the breadth is increased by 7 m. the area is reduced by 360 m 2 πΉπππ π‘βπ πππππ‘β πππ π‘βπ ππππππ‘β ππ π‘βπ ππππ‘. πΏππ‘ π‘βπ πππππ‘β = π πππ ππππππ‘β = π π = 23 + π Given (π β 15)(π + 7) = ππ β 360 (23 + π β 15)(π + 7) = (23 + π )π β 360 (π + 8)(π + 7) = 23π + π 2 β 360 π 2 + 15π + 56 = 23π + π 2 β 360 416 = 8π ππ π = 52π Therefore π = π + 23 = 52 + 23 = 75π 6 For more information please go to: https://icsemath.com/ Q.26 The length of the rectangular park is twice its breadth. If the perimeter of the park is 186 m, find its length and breadth. πΏππ‘ π‘βπ πππππ‘β = π πππ ππππππ‘β = π π = 2π 2π + 2π = 186 4π + 2π = 186 6π = 186 ππ π = 31 π = 62 Q.27 The length of the rectangle is 7 cm more than its breadth. If the perimeter of the rectangle is 90cm, find its length and breadth. πΏππ‘ π‘βπ πππππ‘β = π ππππππ‘β = π π = π+7 πΊππ£ππ 21π + 2π = 90 2(π + 7) + 2π = 90 4π = 76 ππ π = 19 ππ π = 19 + 7 = 26 ππ Q.28 The length of a rectangle is 7 cm less than twice its breadth. If the length is decreased by 2cm and breadth increased by 3cm, the perimeter of the resulting rectangle is 66 cm. find the length and the breadth of the original rectangle πΏππ‘ π‘βπ πππππ‘β = π πππ ππππππ‘β = π π + 7 = 2π Given, 2(π β 2) + 2(π + 3) = 66 2π β 4 + 2π + 6 = 66 2π + 2π = 64 Solving, 2(2π β 7) + 2π = 64 6π = 78 π = 13, π = 2 × 13 β 7 = 19 ππππππ‘β = 13 ππ πππππ‘β = 19ππ Q.29 A man is five times as old as his son. In two yearsβ time, he will be four times as old as his son. Find their present ages. Let the πππβπ πππ = 5π₯ πΌπ π ππβπ πππ = π₯ ππ€π π¦ππππ πππ‘π‘ππ πππβπ πππ = 5π₯ + 2 πππβπ πππ = π₯ + 2 5π₯ + 2 = 4(π₯ + 2) 7 For more information please go to: https://icsemath.com/ π₯ + 6 π¦ππππ = π ππβπ πππ πππβπ πππ = 30 π¦ππ . Q.30 A man is twice as old as his son. Twelve years ago, the man was thrice as old as his son. Find their present ages. Let the π ππβπ πππ = π₯ πππβπ πππ = 2π₯ 12 π¦ππππ πππ πππβπ πππ = π₯ β 12 πππβπ πππ = 2π₯ β 12 2π₯ β 12 = 3 (π₯ β 12) 2π₯ β 12 = 3π₯ β 36 π₯ = 24 = π ππβπ πππ πππβπ πππ = 48 π¦ππππ Q.31 Seema is 10 years elder than Rekha. The ratio of their ages is 5:3. Find their ages. πΏππ‘ π ππβπβπ πππ = π₯ πππππβπ πππ = π₯ + 10 πππ£ππ π₯ + 10 5 = π₯ 3 3π₯ + 30 = 5π₯ 2π₯ = 30 ππ π₯ 15 π ππβπβ² π πππ = 15 π¦ππ . πππππβ² π πππ = 25 π¦ππ . Q.32 5 years ago, the age of Parvati was 4 times the age of her son. The sum of their present ages is 55 years. Find Parvatiβs age. πΏππ‘ π‘βπ ππππ πππ‘ πππ ππ ππππ£ππ‘π = π₯ π¦ππ πππ ππ π ππ = π¦ π¦ππ . π₯ + π¦ = 55 β¦ β¦ β¦ β¦ β¦ β¦ . . β¦ β¦ . . π) Five years before ππππ£ππ‘π = π₯ β 5 π¦ππ . π ππ = π¦ β 5 π¦ππ . Given, (π₯ β 5) = 4(π¦ β 5) π₯ β 4π¦ = β15 β¦ β¦ β¦ β¦ β¦ β¦ β¦ β¦ ππ) π πππ£πππ π) πππ ππ) π₯ β 4 (55 β π₯ ) = β15 5π₯ = 205 ππ π₯ = 44 = ππππ£ππ‘π β² π πππ πππβπ πππ = 55 β 44 = 22 π¦ππππ Q.33 A man is 56 years old and his son is 24 years old. In how many years, the father will be twice as old as his son at that time? πππβπ πππ = 56 π¦ππππ 8 For more information please go to: https://icsemath.com/ πππβπ πππ = 24 π¦ππππ Let in x years, man would be twice the age of son 56 + π₯ = 2( 24 = π₯ ) 56 + π₯ = 48 + 2π₯ ππ π₯ = 8 π¦ππππ Q.34 9 years hence, a girl will be 3 times as old as she was 9 years ago. How old is she now? Let the current age of the ππππ = π₯ πΊππ£ππ, π₯ + 9 = 3( π₯ β 9) π₯ + 9 = 3π₯ β 27 2π₯ = 36 π₯ = 18 π¦ππππ = πππ ππ π‘βπ ππππ Q.35 A man made a trip of 480km in 9 hours. Some part of trip was covered at 45 km/hr and the remaining at 60km/hr. find the part of the trip covered by him at 60km/hr. Let the distance covered at 45 ππ/ βπ = π₯ πΏππ‘ π‘βπ πππ π‘ππππ πππ£ππππ ππ‘ 60 ππ/ βπ = π¦ πππ‘ππ πππ π‘ππππ = 480 ππ. π₯ + π¦ = 480 π₯ π¦ + =9 45 60 Solving 480 β π¦ π¦ + =9 45 60 ππ π¦ = 300 ππ πππ π₯ = 180 ππ Q.36 A motorist travelled from town A to town B at an average speed of 54km/hr. on his return journey, his average speed was 60km/hr. if the total time taken is 9 hours, find the distance between the two towns. Let the distance between town π΄ πππ π΅ = π₯ π₯ π₯ πβπππππππ + = 9.5 54 60 ππ π₯ = 270 ππ. Q.37 The distance between two stations is 300km. two motor-cyclist start simultaneously from these stations and move towards each other. The speed of one of them is 7km/hr faster than that of other. If the distance between them after 2 hours is 34km, find the speed of each motor-cycle π·ππ π‘ππππ = 300 ππ πΏππ‘ π‘βπ π ππππ ππ 1π π‘ ππ¦ππππ π‘ = π₯ πβππ π ππππ ππ 2ππ ππ¦ππππ π‘ = π₯ + 7 π·ππ π‘ππππ πππ£ππππ ππ¦ 1π ππ¦ππππ π‘ ππ 2βπ = 2π₯ π·ππ π‘ππππ πππ£ππππ ππ¦ 2ππ ππ¦ππππ π‘ ππ 2 βπ = 2( π₯ + 7) Therefore 2π₯ + 34 + 2(π₯ + 7) = 300 4π₯ + 48 = 300 9 For more information please go to: https://icsemath.com/ 252 = 63 ππ/βπ 4 πππππ ππ 1π π‘ ππ¦ππππ π‘ = 63ππ/βπ πππππ ππ 2ππ ππ¦ππππ π‘ = 63 + 7 = 70 ππ/βπ π₯= Q.38 A boat travels 30km upstream in river in the same period of time as it travels 50km downstream. If the ratio of stream be 5 km/hr, find the speed of the boat in still water. Let the speed of boat = π₯ ππ/βπ πππππ ππ π π‘ππππ = 5 ππ/βπ πππππ ππ ππππ‘ π’ππ π‘ππππ = π₯ β 5 ππ/βπ ππππππ ππ π‘βπ ππππ‘ πππ€ππ π‘ππππ = π₯ + 5 ππ/ βπ 30 50 πβπππππππ = π₯β5 π₯+5 30π₯ + 150 = 50π₯ β 250 400 = 20 π₯ ππ π₯ = 20 ππ/βπ Q.39 The length of each of the equal sides of an isosceles triangle is 4cm longer than the base. If the perimeter of the triangle is 62cm, find the lengths of the sides of the triangle. πΏππ‘ π‘βπ πππ π = π₯ ππ πππππ = (π₯ + 4) πππππππ‘ππ = 62 ππ πβππππππ (π₯ + 4) + ( π₯) + ( π₯ + 4) = 62 3π₯ + 8 = 62 3π₯ = 54 ππ π₯ = 18 π΅ππ π = 18 ππ, πππππ = 22ππ Q.40 A certain number of candidates appeared for an examination in which one-fifth of the whole plus 16 secured first division, one-fourth plus 15 secured second division and onefourth minus 25 secured third division, if the remaining 60 candidates failed, find the total number of candidates appeared. Let the number of ππππππππ‘ππ = π₯ 1 1 1 ( π₯ + 6) + ( π₯ + 15 ) + ( π₯ β 25) + 60 = π₯ 5 4 4 1 1 1 6 + 60 = π₯ β ( + + ) π₯ 5 4 4 14 π₯ (1 β ) = 66 20 20 × 66 π₯= = 220 6 ππ. ππ ππππππππ‘ππ = 220 Q.41 Raman has 3 times as much money as Kamal. If Raman gives Rs. 750 to Kamal, then Kamal will have twice as much as left with Raman. How much had each originally? Let money with πΎππππ = π₯ 10 For more information please go to: https://icsemath.com/ πβππ πππππ¦ π€ππ‘β π ππππ = 3π₯ 2(3π₯ β 750) = (π₯ + 750) ππ π₯ = 450 π π . πΎππππ βππ 450 π π . π΄ππ π ππππ 1350 π π . Q.42 The angles of triangle are in ratio 2:3:4. Find the angles. π ππ‘ππ ππ πππππ = 2 βΆ 3 βΆ 4 Therefore 2π₯ + 3π₯ + 4π₯ = 180 9π₯ = 180 π₯ = 20 πβπππππππ πππππ πππ 40, 60, 80πππππππ . Q.43 A certain number man can finish a piece of work in 50 days. If there are 7 more men, the work can be completed 10 days earlier. How many men were originally there? Let π₯ πππ πππππ β π€πππ ππ 50 πππ¦π πππ‘ππ π€πππ = 50π₯ πππ πππ¦π π₯ + 7 πππ πππππ β π€πππ ππ 49 πππ¦π πππ‘ππ π€πππ = (π₯ + 7) × 40 Therefore 50π₯ = 40 (π₯ + 7) 5π₯ = 4π₯ + 28) π₯ = 28 ππππππππ ππ ππ πππ = 28 Q.44 Divide 600 in two parts such that 495 of one exceeds 60 of the other by 120. πΏππ‘ π‘βπ π‘π€π ππππ‘π = π₯ πππ π¦ π₯ + π¦ = 600 0.4π₯ β 0.6π¦ = 120 ππππ£πππ π€π πππ‘ π₯ = 480 π¦ = 120 Q.45 A workman is paid Rs. 150 for each day he works and is fined Rs. 50 for each day he is absent. In a month of 30 days he earned Rs. 2100. For how many das did he remain absent? ππππππ¦ = 150 π π ./πππ¦ πΉπππ = 50 π π ./πππ¦ πΏππ‘ π₯ ππ π‘βπ ππ’ππππ ππ πππ¦π π€πππππ πβπππππππ 150π₯ β (30 β π₯)50 = 2100 ππ π₯ = 18 πππ¦π . 11 For more information please go to: https://icsemath.com/
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