HCF and LCM

What is the HCF of 60 and 36?

What is the HCF of 120 and 160?

What is the LCM of 3 and 7?

What is the LCM of 22 and 33 ?

A red light flashes every six minutes. A blue light flashes every 8 minutes. They both flash at the same time. After how many minutes will they both flash at the same time?

A blue light flashes every 8 minutes while a pink light flashes every 54 minutes. Both lights flash together at 2pm. When is the next time that both lights will flash together again?

Mary is organising a charity hot dog sale. There are 18 bread rolls in each packet. There are 15 hot dogs in each packet. Mary buys exactly the same number of bread rolls as hot dogs. What is the smallest number of each packet that Mary can buy?

• 5 packs of bread and 6 packs of hot dogs

• 6 packs of bread and 5 packs of hot dogs

• 6 packs of bread and 4 packs of hot dogs

• 4 packs of bread and 6 packs of hot dogs

Trains leave Bristol

to Cardiff every 15 minutes

to London every 21 minutes.

A train to Cardiff and a train to London both leave Bristol at 11am. At what time will a train to Cardiff and a train to London next leave Bristol at the same time?

• 12.45 am

• 12.45 pm

• 13.45 am

• 13.45 pm

The Highest Common Factor (HCF) of two numbers is 6.

The Lowest Common Multiple (LCM) of the same numbers is 60.

What are the two numbers?

• 12 and 18

• 18 and 24

• 12 and 24

• 12 and 30

Charlie says

"To find the LCM, you just multiply the two numbers together"

Explain why he is not correct

• The answer might be too big

• There might be a smaller number that is a common multiple

• They might not share any numbers

• he is correct