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 [33] 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.