Question

How do you multiply `0.31*69`?

Answer 1

`0.31 * 69 = 21.39`

Explanation:

If you are calculating it in your head, you might be best off doubling `69` five times, subtracting `69`, then dividing by `100`, since `2^5=32`

`69 -> 138 -> 276 -> 552 -> 1104 -> 2208 -> 2139 -> 21.39`

Answer 2

There will be different approaches. All as effective as each other. Here is another one

21.39

Explanation:

`0.31" is "31/(color(magenta)(100)`

Consider `x xx31 =( x xx3xx10) +x`

So `[color(white)(.)(69xx3xx10) +69color(white)(.)]color(magenta)(-:100) =2139/100 = 21.39`