Over the past few days, we have looked at rounding 1 number in order to help us solve an addition question.
Today, we will need to round both in order to solve the question.
Let’s look at one together.
47 + 72
Just like the last few days, start by rounding each number to the nearest 10.
What is 47 to the nearest 10?
How many did I need to add/subtract?
What is 72 to the nearest 10?
How many did I need to add/subtract?
For 47 we added 3.
For 72 we subtracted 2.
Now, we need to solve the question.
50 + 70 = 120
Like the previous days, we need to revert the rounding we did earlier.
So, for 47 we added 3.
If we revert this, we need to subtract 3.
120 - 3 = 117
For 72 we subtracted 2.
If we revert this, we need to add 2.
117 + 2 = 119
Now, we are back to our original question.
47 + 72 = 119
Your turn.
38 + 66
79 + 64
123 + 76
67 + 138