TOPIC
Strand:
Strand unit:
503.2 Round decimals to the nearest whole number.
506
Multiply a decimal (up to 3 places) by a whole number with and without a
calculator.
516.3 Solve problems involving operations with decimals.
1. Multiplying a decimal number up to 2 places by a single-digit whole number.
2. Solving problems involving the multiplication of decimals.
1. Applying and problem-solving: Analysing a problem and planning an approach to solving it,
selecting and applying a strategy to solve multi-step problems involving the multiplication of
decimal numbers.
2. Integrating and connecting: Recognising the use of the rounding and the multiplication of
decimals in the environment.
3. Implementing: Executing the procedures for the multiplication of decimal numbers correctly,
without a calculator, using mental strategies to multiply numbers.
Calculators
Multiply, round, decimal point, tenths, hundredths, thousandths, repeated addition,
estimate, long multiplication
1. Revise multiplication facts and multiplying numbers by multiples of 10.
2. To avoid problems that may be related to positioning the decimal point in an answer, get
students to use rounding and estimation before attempting the computation.
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Choir of number:
Counting in 1s, 10s, 100s, 1,000s each group using a different place value.
Fans:
Show 345, add 100. Show 619, add 10. Show 1368, add 1000. Repeat with lots of numbers.
Revise multiplication and division facts. Multiply a number by 0. What happens?
Counting stick: Counting in different multiples, starting at different numbers.
1. Ideas for calculations involving the multiplication of decimal numbers:
(a) Using a stopwatch find out how long it takes to run 50 metres. Now calculate how long it
would take to run 100/200/500/1000 metres at the same speed.
(b) Find the first 6 multiples of some decimal numbers, e.g. 0·13, 6·89, 0·348, 2·229, 5·789.
(c) Find a number with 2 decimal places that will multiply with a 1-digit number to make 10.
Is there more than one way of doing it?
(d) Explore why shops often use 99c in their prices. Can you find 10 items in a local shop/
catalogue ending in 99c?
Find the cost of each item if the rugby jersey costs €41·97.
1. The Harry Potter book is one-third less expensive than the rugby jersey. (€13·99)
2. The mug is €37·98 cheaper than the jersey. (€3·99)
3. The scarf is €21·98 cheaper than the jersey. (€19·99)
4. The T-shirt is €3·99 cheaper than the scarf. (€37·98)
5. The jar of pencils is 4 times more expensive than the T-shirt. (€15·96)
6. The pencil case is 3 times more expensive than the mug. (€11·97)
7. The birthday card is 50c less than the mug. (€3·49)
8. The Irish book is 5 times more expensive than the birthday card. (€17·45)
Lower attainers:
Extra practice on rounding, estimating and multiplication.
Higher attainers:
1. Word problems involving decimal numbers.
2. Rounding to the nearest whole number with numbers that have up to 3 decimal places.
3. Activity C on page 89 requires a careful reading of the diagram.
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Topic
Topic
13
13
1. Make each of these numbers 10 times bigger.
1. Round each of the following to the nearest whole number.
(a) 12
(b) 1.7
(c) 23
(d) 2.33
(e) 4.06
(f) 0.79
(g) 0.088
(h) 0.005
(i) 1.268
(a) 2.042
(b) 0.552
(c) 3.06
(d) 5.6
(e) 3.091
(f) 12.532
2. Make each of the following number 1,000 times bigger.
2. Make each of these numbers 100 times bigger.
(a) 6
(b) 13
(c) 39
(d) 0.8
(f) 12.689
(g) 2.094
(h) 0.001
(i) 23.165
(e) 4.23
(b) 15
(c) 35
(d) 1.6
(e) 0.03
(f) 1.06
(g) 2.009
(h) 1.462
(a) A racetrack is 0.9km in length. How far would an athlete travel if they did 36 laps of the track?
3. Round each of these decimals to the nearest whole number.
(a) 0.774
(a) 2
(b) 1.098
(c) 1.601
(d) 2.5
(e) 15.288
(f) 20.55
(g) 80.864
(h) 82.081
(i) 106.059
Round your answer to the nearest kilometre.
(b) How much short of 50 is 48.063?
(c) Find the sum of the following numbers: 6, 1.36, 0.306 and 0.63.
(d) What is the difference between €123.31 and 87c?
(e) Increase 0.468 by 25.
4. Estimate and then multiply
(a) 7.149
(b) 8.762
(c) 12.442
(d) 16.788
×
×
×
×
8
6
7
(f) Make 0.012 sixty-three times larger.
5
(g) A silo can hold 53.6 kg of grain. How many bags of 4kg each can be filled from the silo?
(h) If an orange weighs 0.256 kg, what is the weight of a bag of 6 oranges of the same weight?
Round your answer to the nearest kilogramme.
5. Estimate and then multiply
(a) 0.885 × 14
(b) 1.669 × 12
(c) 2.043 × 12
(d) 5.065 × 10
(e) 8.889 × 12
(f) 10.053 × 15
over 20 nights?
Name: _______________________________________
© Folens Photocopiables
Date: ___________________
(j) Gillian spends 1 14 hours per night at her homework. How long does she spend at her homework
© Folens Photocopiables
Name: _______________________________________
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(i) How many minutes in 1.75 hours?
Date: ___________________
137
Fractions and Percentages: Converting decimals to fractions and percentages
Measures: Using multiplication of decimals in the unitary method, decimal values of units of
measurement in Length, Weight, Capacity and Time
PE: Using decimal number to record time and distance
Use a newspaper to find examples of the use of decimals in the environment. Are there
examples in the financial section, classified ads, advertisements or sport section? Cut out some
examples and compare them with the other examples found by classmates.
Notes
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