Subtraction Using Compensation — Let's Practice!

Subtraction Using Compensation — Let's Practice! exercise

• Why does Razzi suggest making one of the numbers "friendlier" before subtracting?

  Hints

  Think about why making one number friendlier can simplify the subtraction.

  Think about rounding to the nearest 10 or 5 and how it affects the subtraction process.

  Solution

  Making one of the numbers friendlier helps us to adjust the numbers in a way that makes the calculation easier.

• What would be the result after subtraction using compensation?

  Hints

  Remember, whatever you have done to one number must also be done to the other number.

  When making 15 friendlier, we add 5 to it to round it to 20.

  Then we also add 5 to 8.

  Solution

  The steps are:

  1.First choose to make one number friendlier. In this case, making 15 friendlier would make it simpler.

  2.Change the friendlier number to an easier value. Round 15 to the nearest 10, which is 20.

  3.As we added 5 to 15, we need to add 5 to 8. 8 + 5 = 13

  4.Last, subtract the changed numbers. If 20 - 13 = 7, then 15 - 8 = 7

• How many cookies will Mr. Squeaks have after each subtraction?

  Hints

  If you round one number down, adjust the other number accordingly.

  45 - 21 = ?

  If we round down 21 to 20, we take away 1.

  We take away 1 from 45 as well, and we have 44.

  44 - 20 = 24

  After subtracting, double-check your answer.

  Solution

  45 - 21 = 24

  65 - 12 = 53

  18 - 9 = 9

  72 - 28 = 44

• Solve the problem.

  Hints

  Identify Friendlier Number: Choose to make the number 37 friendlier.

  Adjust Friendlier Number: Adjust 37 to a more convenient value, such as 40.

  Solve 40 - 22 to find the answer.

  Solution

  Mr. Squeaks will have 18 marbles left after subtracting 19 marbles from 37 using compensation.

  1. Choose a friendly number close to 37. Let's choose 40.
  2. Since we add 3 to 37, we need to add 3 to 19, which makes it 22.
  3. Subtract the adjusted numbers. 40-22=18

• Solve the subtraction using compensation.

  Hints

  We can start by rounding 12 to the nearest tens place.

  What number is this?

  When we subtract 2 from 12, we also have to subtract 2 from the other number.

  3 - 2 = ?

  Solution

  1.Start by making 12 friendlier.

  2.Round 12 to 10 by taking away 2.

  3.Next, we need to take away 2 from 3.

  4.We now have 10 - 1.

  5.10 - 1 = 9 therefore 12 - 3 = 9

• Can you solve the subtraction using compensation?

  Hints

  Consider rounding one of the numbers to a convenient value to simplify the subtraction process.

  If we make 25 become 30 by adding 5, we also have to add 5 to 8.

  Solution

  25 - 8 = 17

  1.Add 5 to 25 to make it 30.

  2.Then add 5 to 8 as well. It makes it 13.

  3.Now subtract 30 - 13 = 17

  4.30 - 13 =17 therefore 25 - 8 = 17