The distributive property and mixed operations · Usually met around P4
×9 and ×99
×99 is ×100 take away one lot.
How to do it
Method
×99 is ×100 take away one lot
47 × 99 = 4700 − 47 = 4653
Another way
Column multiplication
47 × 9 = 423, 47 × 90 = 4230, 423 + 4230 = 4653
In full
×9 is ×10 take away one lot: 47 × 9 → 470 − 47 = 423. ×99 is ×100 take away one lot: 47 × 99 → 4700 − 47 = 4653. This is the distributive property: 47 × 99 = 47 × 100 − 47 × 1. You can also multiply in columns.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
93 × 9
Show the answer and working
Answer: 93 × 9 = 837
93 × 9: ×9 is ×10 take away one lot, 93 × 10 = 930, 930 − 93 = 837
Example 2
54 × 9
Show the answer and working
Answer: 54 × 9 = 486
54 × 9: ×9 is ×10 take away one lot, 54 × 10 = 540, 540 − 54 = 486
Example 3
42 × 9
Show the answer and working
Answer: 42 × 9 = 378
42 × 9: ×9 is ×10 take away one lot, 42 × 10 = 420, 420 − 42 = 378
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