Start here

Use the model to solve the first problem. Then try these quick review questions from earlier lessons.

1. 1

   Same stepsFinish what the group started. Use the model above, step for step. 🔊 Listen 💡 Hint

   Try it together — then prove it:

   1. Use prime factors to find the GCF of 48 and 36. Then explain why the method works.
   2. Write 48 and 36 as products of primes. (48: 2 × 2 × 2 × 2 × 3 → 36: 2 × 2 × 3 × 3)
   3. Multiply the primes both numbers share. (2 × 2 × 3 = 12)
   4. Why do we multiply only the primes both numbers share? (A common factor must divide both numbers. Only the shared primes are in both 48 and 36.)

   Show your work
2. 2

   Quick reviewWhich expression is equivalent to 5x + 2x? 🔊 Listen 💡 Hint

   1. A7x
   2. B7x²
   3. C10x
   4. D52x

   How do you know?
3. 3

   Quick reviewAre 3(n + 2) and 3n + 6 equivalent? Test with n = 4. 🔊 Listen 💡 Hint

   1. ANo — one is 18 and one is 14
   2. BYes — both equal 18
   3. CYes, but only when n = 0
   4. DYou cannot test with a number

   How do you know?
4. 4

   Quick reviewSimplify 6a + 4 − 2a. 🔊 Listen 💡 Hint

   1. A2a + 4
   2. B4a + 4
   3. C4a
   4. D8a

   How do you know?

Try these on your own

Choose an answer. Then explain how you know.

1. 5

   Think it throughWhat is the GCF of 48 and 36? 🔊 Listen 💡 Hint

   1. A4
   2. B6
   3. C12
   4. D144

   Why is that the answer?
2. 6

   Think it throughWhat is the LCM of 6 and 8? 🔊 Listen 💡 Hint

   1. A2
   2. B14
   3. C24
   4. D48

   How do you know? Give a second reason as well.
3. 7

   Think it throughA problem asks when two repeating schedules meet again. Which do you use? 🔊 Listen 💡 Hint

   1. AThe least common multiple
   2. BThe greatest common factor
   3. CEither one works
   4. DNeither — you list factors

   Explain your thinking. What would have to change for a different choice to be right?
4. 8

   Back to the modelBoth problems say “common.” How do you decide whether a problem wants the GCF or the LCM? 🔊 Listen 💡 Hint

Sort it again — on paper this time

Write the letter of the group each one belongs in.

• What is the largest number of identical combo packs?
• When will both classes fall in the same week again?
• How many equal groups can I split both stocks into?
• Hot dogs come in 10s and buns in 8s — when do they match?
• The answer is never bigger than either number
• The answer is never smaller than either number

Use the words

Fill each blank with a word from the bank.

• A number that divides another exactly, with no remainder, is a ___.
• What you land on counting by a number are its ___.
• The largest number that divides both is their ___ ___ ___.
• The smallest number both numbers reach is their ___ ___ ___.

Explain the thinking

1. 9

   Find the mistakeRead the mistake. Explain what went wrong, then show the correct step. 🔊 Listen 💡 Hint

   The mistake: A common mistake is reaching for the wrong tool: listing FACTORS for a problem about repeating cycles.
2. 10

   Say moreHow did you find the factors that 24 and 36 share, and how did you decide which one is the GCF? 🔊 Listen 💡 Hint
3. 11

   Write your ownWrite your own problem about this situation, then solve it and show the answer. The situation: Mission Control sorted the factors of 56 and the factors of 48 into two overlapping rings. The numbers that divide BOTH 56 and 48 sit in the middle, where the rings cross. 🔊 Listen 💡 Hint

   Show your work

Last check

These two come from Lesson 6.6. If they are shaky, that is the lesson to revisit — not this one.

1. 12

   Show what you knowExplain your thinking — Two supply runs repeat every 6 weeks and every 8 weeks, and both happen this week. When will they next happen in the same week? 🔊 Listen 💡 Hint

   1. AWeek 2, the greatest common factor of 6 and 8
   2. BWeek 14, because 6 + 8 = 14
   3. CWeek 24, the least common multiple of 6 and 8
   4. DWeek 48, because 6 × 8 = 48

   Explain your choice.
2. 13

   From Lesson 6.6Explain your thinking — Which expression is equivalent to 6n + 4 + 3n − 1? 🔊 Listen 💡 Hint

   1. A9n + 3
   2. B9n + 5
   3. C18n + 4
   4. D63n

   How do you know?
3. 14

   From Lesson 6.6Test it: what does each expression equal when h = 5? 🔊 Listen 💡 Hint

   1. AA = 50 and B = 60
   2. BBoth equal 60
   3. CA = 60 and B = 55
   4. DBoth equal 90

   How do you know?

Check your progress

Choose the box that best describes how you feel about each skill.