Question

I’m trying to show my grand daughter how to get to the correct answer. Can you show me how you got the answer to 40.99*2.1=

Answer 1

hmmm when it comes to doing operations with decimals, we can hmmm say for this case, the product, we can just toss the dot and perform the multiplication straight up with only 4099 * 21, and then we'll include the decimal point.

`40.\underline{99}* 2.\underline{1} \\\\[-0.35em] ~\dotfill\\\\ 4099* 21\implies \begin{array}{rllll} 4099\\ * 21\\\cline{1-1} 4099\\ +8198~~\\ \dotfill\\ 86079 \end{array}\hspace{5em}86\underline{079}\implies 86.079`

now, let's notice, our product was really 86079, then we go back, 40.99 has two decimals, and 2.1 has one decimal, so we have a total from both of three decimals, so our product must have also three decimals, so we move the dot from the right to the left by 3 slots.