The kettle in Keith’s kitchen is 80% full. After 20% of the water in it has been poured out, there are 1152ml of water left.

What volume of water does Keith’s kitchen kettle hold when it is full?

3 answers

When the kettle is full, it holds 1800ml of water.
80% = 80 / 100 = 0.8

20% = 20 / 100 = 0.2

When 20% of water is poured out of it, 0.8 • 0.2 = 0.16 volume will be poured.

New volume of water will be:

0.8 V - 0.16 V = 0.64 V

Or:

100% - 20% = 80%

New volume of water will be

80% of 80% volume = 0.8 • 0.8 V =

= 0.64 V

This means:

0.64 V = 1152

V = 1152 / 0.64 = 1800 mL
volume of kettle ---- x ml

amount of water in kettle at start = .8x
after 20% of that was removed, amount left = (.8)(.8x) = .64x

.64x = 1152
x = 1152/.64 = 1800 ml