Explain how constant difference can make written calculations more efficient | Exit Quiz | Oak National Academy

Which of the following expressions is not equivalent to the others?

• 57 − 51

• 56 − 50

• 55 − 45

• 54 − 48

• 53 − 47

Answer explanation

All the expressions have a value of 6 except for 55 − 45 which has a value of 10

Which of the following expressions is not equivalent to the others?

• 248 − 203

• 249 − 204

• 250 − 205

• 250 − 206

• 252 − 207

Answer explanation

All the expressions have a value of 45 except for 250 − 206 which has a value of 44

Match the expression with the adjustment to the minuend and subtrahend that will make them more efficient for calculation.

• 52 − 37

• − 1

• 69 − 43

• − 2

• 65 − 47

• + 3

• 81 − 24

• + 1

Answer explanation

All the adjustments have turned either the subtrahend or minuend into a multiple of ten. For example, subtracting 1 from both 81 and 24 makes 80 − 23 which is easier to complete mentally.

Use adjustment of the minuend and subtrahend followed by your understanding of place value. 20.58 − 5.96 = ___

Answer explanation

20.58 − 5.96 = 20.62 − 6 = 14.62

Use adjustment of the minuend and subtrahend followed by partitioning to calculate the following subtraction. 70,559 − 54,504 = ___

Answer explanation

70,559 − 54,504 = 70,555 − 54,500 = 70,555 − 50,000 − 4,000 − 500 = 20,555 − 4,000 − 500 = 16,555 − 500 = 16,055

Use adjustment followed by a written procedure to calculate the following. 40,000 − 2,654 = ___

Answer explanation

40,000 − 2,654 = 37,346