Page 103 - Math Smart - 7

I have 8.3 kg of flour. I used 4.5 kg of the flour. How much flour
I
do have left?
O Which expression would you use if you wanted to calculate exactly how
much flour you have left?
a) 8.3-4.5 b) 8.3 + 4.5 c) 8.3 x 4.5 d) 8.3+ 4.5
O Calculate the exact amount of flour you have left.

O Which expression would you use to estimate how much flour you have
left?
a) 8-4 b)9-4 c)9-5 d)8-5
O Calculate the estimated amount of flour you have left.
O Compare the exact amount of flour to the estimated amount of flour.
Are the two answers the same?

Estimation helps us to work out the answer to a problem mentally or quickly. A
good estimation is close to the actual value and helps us to check the validity of
our answer.
There are times when you work out problems and the answer is a decimal. It does
not make sense to have a decimal for some quantities.

have worked
out that need one and
I
a halP (1.5) tins oQ paint
to paint my bedroom.

You cannot
buy hal(^ a tin
oP paint!

Sometimes the decimal may need to be rounded up or down to give an answer
that is appropriate. For example, the answer could be 1.5 tins of paint, but you
cannot buy half of a tin of paint. You would have to round the answer up to
2 tins of paint.

o