Pls help number 18 and 20

Total mass of materials = 4.8kg

For gravel

55% of the materials are gravel

So we have

55/100 × 4.8 kg

= 2.64kg

For sand

30% of the materials are sand

We have

30/100 × 4.8

= 1.44kg

For cement

The remaining materials were cement so we add the masses of both the sand and gravel and subtract it from the total mass

That's

4.8 - (2.64 + 1.44)

4.8 - 4.08

= 0.72 kg

She earns £ 800 per week

She receives a raise of 7.5% which is

100 + 7.5 = 107.5%

So we have

107.5 / 100 × £ 800

= £ 860

She now earns £ 860 per week

Hope this helps you

option a is correct.

step-by-step explanation:

scale factor: it is used to find proportional measurements.

proportions means having the same ratio.

scale factor is the ratio of the model measurement to the actual measurement in a simplest form.

or we can say that the ratio of any two corresponding lengths in two similar geometric figures

if the scale factor is more than 1, then it is an enlargement,

if the scale factor less than 1, then it is a reduction.

given the two geometric figure:

by definition of proportions, we have