Question

amy was doing her math homework and got an answer of 1.683 for the problem 5.61x3. her friend ruth knew immediatelty that the answer was wrong, without doing any calculations.How did she know

Answer 1

She knew because 5.61 is a bigger number then 1.683. When your multiplying your going to make it bigger, so when doing 5.61*3 just do an estimate and you get a number bigger then 1.683!

Answer 2

When you look at the problem . . . . . 5.61 x 3

you know right away that the answer must be bigger than 5.61,
because the problem means taking 5.61 three time.

Also, multiplication can be done in either direction, so the problem
is the same as starting with 3 and taking it 5.6 times, so the result
must be bigger than 3 .

Amy's answer of 1.683 is smaller than 5.61 and also smaller than 3,
so there's no way it can be correct.