Maths question - estimating

[Strugglingtodomybest]

Can anyone help with this question please as I and my two DS's can't answer it correctly according to MathsWatch.

By rounding to one significant figure, estimate 798/(8x41)

Round each number to one significant figure:
798 becomes 800.
8 becomes 10.
41 becomes 40.

So you have 800/400, so the answer is approximately equal to 2.

Can be interesting to use a calculator to see how close the true answer is.

Isn’t 8 rounded to 1 significant figure 8 not 10?

Well, there are 3 questions and we've got at least 1 wrong and I thought it was that one as it was the most complicated, but we put 2 too.

The other two are:
98 divided by 11 - for which we answered 10
764 divided by 19 - for which we answered 40

Are they right?!!

This is the problem with MathsWatch, it doesn't tell you which you've got wrong, just that you have some answers incorrect.

Thanks for helping btw, this is driving me mad!

They look right to me.

What did you get for the answer in the question in the OP?

I get 800/(8*40)

800/320 which cancels down to 5/2 or 2.5 depending on what format they want the answer in.

I’ve just seen you answered 2. Should have read properly.

I used same method as @wanderings

8 is already 1 significant figure though. You don’t need to do anything to it to make it 1s.f.

I’d say

2.5
10
38

You’re rounding the answer too and I don’t think you should be.

I make it 40 rather than 38.

Isn’t it 800/20?

I get 800/320 as well. As Rafals said 8 is already 1 s.f.

Thanks everyone, I will try them all!

the answer is 2.5 because its correct on mw