My daughter brought home this question:

How does knowing 28=30-2 help you find 13+28?
Any ideas?

Because then you can figure out what 11 more than 30 is. That is easier than trying to add 13 and 28 in your head.

Yes, it is a matter of grouping:

13+ 28= (11+2)+28= 11 + (2+28)= 11+30

length in feet and inches

Certainly! Knowing that 28 equals 30 minus 2 can definitely help you find the sum of 13 and 28. Let me explain.

To work through this problem, we can use the concept of substitution. Since we know the value of 28, we can substitute it in place of 30 minus 2 in the equation 13 + 28.

So, instead of solving the equation 13 + 28, we can substitute 30 minus 2 in place of 28, which gives us 13 + (30 - 2).

Now, we need to simplify the equation. First, we can perform the subtraction inside the parentheses, which gives us 13 + 28.

By substituting the value of 28 as 30 minus 2, we have essentially broken down the addition problem into smaller components. We can now solve the subtraction problem (30 minus 2) and use the result to add to 13.

Performing the subtraction, 30 minus 2 equals 28. So, we can replace 30 minus 2 with 28 in the equation, giving us 13 + 28.

Finally, with the simplified equation, we can add 13 and 28 together. The result is 41.

Therefore, knowing that 28 equals 30 minus 2 helps us find the sum of 13 and 28 by breaking down the addition problem into simpler parts and substituting the known value in place of the variable.