Related Calculations Flashcards

All 5 cards in this deck

What are the steps to use a given calculation to work out a related one?

e.g. given $46 \times 12 = 552$, find $4.6 \times 1.2$

1. Compare each number: $46 \div 10 = 4.6$ and $12 \div 10 = 1.2$
2. Apply the same changes to the answer: $552 \div 10 \div 10$
3. Answer: $5.52$

If one number in a multiplication is multiplied by 10 and the other is divided by 10, what happens to the answer?

It stays the same.
e.g. $23 \times 17 = 230 \times 1.7$

In a division, what happens to the answer if you divide the divisor by 10?

e.g. $391 \div 17 = 23$, so what is $391 \div 1.7$?

The answer is multiplied by 10.
$391 \div 1.7 = 230$

True or false? If $23 \times 17 = 391$, then $2.3 \times 1.7 = 39.1$.

False. Both numbers are 10 times smaller, so the answer is 100 times smaller: $3.91$.

How do the digits of the answer change when you use place value to derive a related calculation?

They do not change — only the position of the decimal point changes.
e.g. $546 \times 43 = 23478$ and $54.6 \times 4.3 = 234.78$