Whole-number Strategies and Estimation

≈ 35 min

Whole-number Strategies and Estimation

Strong Grade 7 number work is not just long multiplication. Break numbers apart by place value, use compatible numbers for mental division, and estimate before an exact calculation. The distributive law explains a useful strategy: $23\times6=(20\times6)+(3\times6)$ . Estimation tells you whether the exact answer is reasonable.

Worked example

$398+207$ is about $400+200=600$ . Exactly, $398+207=605$ . The estimate warns us that an answer such as 6 050 would have the wrong place value.

Exam method

Estimate with friendly numbers. 2. Choose a strategy or written method. 3. Compare the exact answer with the estimate.

Calculate $46\times7$ .

Estimate $612+189$ by rounding each number to the nearest hundred.

Which estimate is most sensible for $49\times21$ ?

1 000

100

10 000

In $23\times6=(20\times6)+(3\times6)$ , the number 23 was split into ______ and ______.