Question

How do you evaluate `4.2 times 8.1`?

Answer 1

`34.02`

Explanation:

`color(brown)("This is one method of several")`

Don't like decimals so lets get rid of them.

Write `4.2" as "42xx1/10`
Write `8.1" as "81xx1/10`

So `4.2xx8.1" "=" "42xx81xx1/10xx1/10`

But `1/10xx1/10=1/100`
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
`color(blue)("Doing the calculation by splitting the 42 into 40 and 2")_`

`40xx81=3240`
`color(white)(4)2xx81=ul(color(white)(3)162) larr " add"`
`color(white)("ddddddddd")3402`

Now we apply the `xx1/100` giving

`3402xx1/100 = 34.02`