Multiply One Digit by Multiples of 10

How the lesson starts: Multiply One Digit by Multiples of 10

Zookeeper Kai
Hi, zoo helper! Zookeeper Kai feeds the hungry monkeys. Bananas come in bunches of 10. Each monkey eats 20 bananas a week. How many do 3 monkeys need?
Count the tens
Each rod here is a bunch of 10. Monkey 1 gets 2 tens. Monkey 2 gets 2 tens. Monkey 3 gets 2 tens. That's 6 tens. 6 tens is 60. So 3 × 20 = 60!
Let's find 4 × 30
4 monkeys each get 30 bananas. 30 is 3 tens. So think 4 × 3 = 12. That's 12 tens. 12 tens is 120. So 4 × 30 = 120! Watch out: don't drop the zero. 12 would be way too few bananas.