Question

What 2 numbers should be used to find 231 - 198 using the 10 method for subtracting quickly in your head?

Answer 1

Answer: "Count 2 and then count 31 more."

Step-by-step explanation:

We have the equation:

231 - 198

Now, the negative number is kinda ugly, so i will write it as:

200 - 2 = 198

Is a lot easier work with 200 and 2, than with 198.

Then the equation is now:

231 - (200 - 2)

And the left number we also have a "200", so it can be written as:

200 + 31 = 231

As this is a sum, we can ignore the parentheses.

200 + 31 - 200 + 2

31 + 2

Then the correct option is:

"Count 2 and then count 31 more."