Adding Tens and Ones

Mugisha counts 23 bottle caps in his tin. Keza counts 15 in her pocket.

They pour them all into one bag. How many caps are in the bag now?

You can work this out. Let's do it together, step by step.

You already know this bit. Look:

23 is 2 tens and 3 ones. 15 is 1 ten and 5 ones.

When you add, keep tens with tens and ones with ones. Never mix them up.

Step 1. Add the ones. 3 ones + 5 ones = 8 ones.

Step 2. Add the tens. 2 tens + 1 ten = 3 tens.

Step 3. Put them back together. 3 tens and 8 ones is 38.

So 23 + 15 = 38. Mugisha and Keza have 38 bottle caps in the bag.

Ones: 2 + 5 = 7.

Tens: 4 tens + 3 tens = 7 tens, and 7 tens is 70.

70 and 7 make 77. So 42 + 35 = 77.

Uwase has 51 beans. She finds 6 more under the table.

The 6 is only ones, so it goes in the ones column. Put the 6 under the 1, never under the 5!

Ones: 1 + 6 = 7. The 5 tens have nothing to add, so they stay 5 tens.

51 + 6 = 57.

30 + 40 is easy. 3 tens + 4 tens = 7 tens. And 7 tens is 70.

The ones are 0 and 0, and 0 + 0 = 0. So the answer ends in 0.