# Sarin learns rate of change in school Part 3 (Math Question)

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The blog postings are about the Singapore Math. The readers can learn from the postings about Solving Singapore Primary School Mathematics. The blog presenting the Math Concept, Math Questions with solutions that teaches in Singapore Primary Schools. You or the kids can learn deal with Math Modeling, Problem Sum from Lower Primary School to Upper Primary School level. This posting is an upper primary school math question on Volume and Flow Rate.

Read the posting on Sarin learns rate of change in school (Math Concept) to learn about concept of rate of change.

You can read the posting on Sarin learns Perimeter, Area and Volume in school(Math Concept) to learn the concept of volume.

Upper primary school mathematics question UPQ219

Two rectangular tanks A and B measures 40 cm by 20 cm by 40 cm and 50 cm by40 cmby 45 cm respectively. Water is being filled by Tap P and Q at a rate of 1.2 litres/min and 5 litres/min in Tank A and Tank B respectively. At 8 a.m., Tap P was turned on first.

(a) What is the height of the water level in Tank A after 10 minutes?

(b) At 8.10 a.m., Tap Q was then turned on. At what time will the height of the water level in both tanks equal?

Solution:

The flow rate of tape P = 1.2 l/min

The volume of water in tank A after 10 minutes = 1.2 × 10 = 12 l

The height of the Water level in tank A after 10 minutes = 12000 ÷ 40 ÷ 20 = 15 cm

The flow rate of tape Q = 5 l/min

The height of the water level in tank B after 10 minutes = 50000 ÷ 50 ÷ 40 = 25 cm

The rate of change of height in tank A = 15 ÷ 10 = 1.5 cm/min

The rate of change of height in tanks B = 25 ÷ 10 = 2.5 cm/min

The different in height in the two tanks = 2.5 – 1.5 = 1 cm/min

Tank A had 15 cm height of water when tank B start to fill

The time require to have same height level in the two tanks = 15 ÷ 1 = 15 min

At 8.25 a.m., both tanks had same water height level.