Question Same time, same distance
Today’s problem — free all day, every step. Every day has one.
Two tanks — same flow rate, equal height
Two rectangular tanks are shown below. At first, Tank A was empty and one third of Tank B was filled with water. Both taps were turned on at the same time and water from both taps flowed at the same rate of 1.2 litres per minute. How long did it take for the height of the water to be the same in both tanks?
Show the answerHide the answer
Answer
See all 8 steps
MathBrush is being tested with a few parent groups, and every solution on the site is open to them — one household, all children. If you were given a code, it goes in once and this device remembers it.
I have a code → See the free ones
65 worked examples are free without a code, two from every pattern. No account, either way.
About this method
Two travellers spend the same time, or cover the same distance.
In this one. The same volume per minute poured into a smaller base area makes a faster rise, so the height gap between the two tanks shrinks at a fixed number of centimetres each minute — find the gap, find the rate it closes at, and divide.
How to spot it
Two travellers set off together or one chases another, with constant speeds and a question about who is ahead, when they meet, or how far apart they are.
Common mistake
Children divide the whole distance by the difference in speed instead of dividing the gap between the travellers, or compare distances covered over different lengths of time.
Get the free patterns and skills booklet
Patterns and skills booklet
Worked examples of all 33 patterns and skills, in a booklet you can print.