Math CentralQuandaries & Queries


Question from isaac, a student:

I am struggling in math & I need help on multiplying 3.8 x 2.2. Can you helpme

Hi Isaac,
Decimals come with many rules and can sometimes be frustrating.
When multiplying decimals, you need to add their places,

4.4 x 2.2 = (1place+1place)

  9.68 = (2places)

The rest should be remembering rules of multiplying. Hope this helps :)


I would do this slightly differently. Ignore the decimals to get $44 \times 22 = 968.$ That's what Melanie did and then added (1place + 1place = 2 places) to decide where to place the decimal. After obtaining the 968 I would look at the original problem, $4.4 \times 2.2$ and say that's about $4.5 \times 2$ which is $9$ so the decimal must go after the $9$ to hence $4.4 \times 2.2 = 9.68.$


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