# Video: Hundred Square Grids

In this video, we will learn how to count onward in tens and ones on hundred squares to add two-digit numbers.

04:58

### Video Transcript

Hundred Square Grids

In this video, we will learn how to count onwards in 10s and ones on a hundred square to add two-digit numbers. Let’s take a closer look at the numbers on a hundred square grid. We can read the numbers from left to right, one, two, three, four, five, six, seven, eight, nine, 10. We’re adding one each time. And if we count backward, 10, nine, eight, seven, six, five, four, three, two, one, we’re subtracting one each time.

What happens when we count downwards on a hundred square? Five, 15, 25, 35, 45, 55, 65, 75, 85, 95, the numbers are increasing by 10 each time. We’re adding 10. And if we count upwards, we’re subtracting 10 each time, 99, 89, 79, 69, 59, 49, 39, 29, 19, nine. To add four to 46, we need to count forward, one, two, three, four. 46 add four equals 50.

What happens if we want to add a multiple of 10 to a number? How would we add 50 to 33? We know that 50 has five 10s. And to add 10, we need to count downwards, 10, 20, 30, 40, 50. 33 add 50 equals 83. To add 10, we counted downwards on the hundred square. 50 is five 10s, so we counted downward five squares.

Find the sum of 33 and eight. Use the hundred square to help you.

We need to start at number 33 on the hundred square. And we need to add eight, which means we need to count forward eight, one, two, three, four, five, six, seven, eight. The sum of 31  and eight is 41. We started at 33 on the hundred square and we counted forward eight squares. Let’s practice one more example of adding using a hundred square.

50 people are going to a party. Then, 15 more people decide to go. How many people are going to the party? Find the number by using the chart to count.

We know that 50 people are going to a party. Then, 15 more people decide to go. So, we need to start counting at 50 on a hundred square and count forward 15 squares. 15 is made from a 10 and a five. We can quickly add 10 to 50 by counting down one square on the hundred square. We know that 50 plus 10 is 60.

Now we just need to add the five from 15. If we start at 60 and count forward five spaces, or five squares, we land on 65. 50 plus 15 equals 65. To add 15 to 50, we counted down one square to add 10 and across five to add five. 50 plus 15 equals 65.

In this video we’ve learned how to count forward in 10s and ones on a hundred square to add two-digit numbers.