Student Name_____________________________!
Date______________
Learning Target # 11 : I can add and subtract fractions with unlike denominators.
Aim : I can convert fractions so they have the same denominators by determining their
LCM and then add or subtract them.
DO-NOW
Sophia’s birthday is 14 days away. Her best friend Susan’s birthday is 5
weeks away. How many days are there between Sophia and Susan’s
birthday?
NOTES
UNLIKE DENOMINATORS
QUESTION: “How do we add or subtract fractions with unlike denominators?”
ANSWER: “We must find the Least Common Denominator in order to find a common
denominator.”
STEP 1: Look at the problem and make a list of the first ten multiples of both your denominators.
STEP 2: To find the LCD, circle the common multiple that has the lowest value.
STEP 3: Set up new fractions using your LCD. (Multiply the numerators by whatever the
denominator was multiplied by).
GUIDED PRACTICE
HOW DO WE FIND THE LEAST COMMON DENOMINATOR?
1) Write the first ten multiples for 3 and 5. Then circle the one with the lowest value.
10 Multiples of 3:
10 Multiples of 5:
Student Name_____________________________!
2)
Date______________
Write the first ten multiples for 4 and 6. Then circle the one with the lowest value.
10 Multiples of 4 :
10 Multiples of 6 :
3) In the school kitchen during lunch, the timer for pizza buzzes every 14
minutes. The timer for hamburger buns buzzes every 6 minutes. The two
timers just buzzed together. In how many minutes will they buzz
together again?
INDEPENDENT PRACTICE
Write 10 common multiples for each number. Then circle the LCM.
1)
Find the LCM of 4 and 5
Common multiples:
2)
Find the LCM of 12 and 8.
Common multiples:
Student Name_____________________________!
Date______________
partner task
your partner’s name______________________________
A store will celebrate the release of a new game system by giving free gifts to some of its
customers. On the day the game system is released, every 5th customer will receive a free video
game and every 12th customer will receive a free game system.
1. What is the total number of customers who will receive a free video game before a
customer receives the first free game system? Show or explain how you got your answer.
2. Who is the first customer to receive both a free video game and a free game system?
3. Of the first 50 customers, what is the total number of customers who will receive a free
gift? Show or explain how you got your answer.
4. If 200 customers visit the game store on this day, what is the total number of customers
who will receive both a free video game and a free game system? Show or explain how
you got your answer.
HOMEWORK
Redskins radio give away a McNabb jersey to every 100th caller. Every 30th caller
received free tickets to the game. How many callers must get through before one of
them receives both a coupon and a concert ticket.