Class 9 Work and Rate Equations — practice questions with answers
Linear Equations · 5 sample questions from the school syllabus. Try each one, then open the answer and the worked solution.
1. A tank holds 500 litres. A pump fills 20 litres a minute. Which equation gives the water W (litres) after t minutes, starting empty?
- AW = 20t
- BW = 500 - 20t
- CW = 20 + t
- DW = 500t/20
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Answer: A) W = 20t
Water grows by 20 L every minute from zero: W=20t.
2. The graph of W = 500 - 25t (litres left in a draining tank) meets the t-axis at which point?
- A(0, 500)
- B(25, 0)
- C(20, 0)
- D(500, 0)
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Answer: C) (20, 0)
On the t-axis W = 0: 500=25t, t=20. (0, 500) is where it meets the W-axis.
3. A tank is filled at a rate that makes W = 25t + 100. How much water was in it at t = 0?
- A25 litres
- B125 litres
- C0 litres
- D100 litres
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Answer: D) 100 litres
Put t=0: W=100.
4. A carpenter and his helper earn Rs 1,800 a day together. The carpenter earns Rs 600 more than the helper. How much does the helper earn?
- ARs 1,200
- BRs 900
- CRs 600
- DRs 750
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Answer: C) Rs 600
h+(h+600)=1800, 2h=1200, h=600.
5. Sana can type p pages an hour. In 3 hours she types 18 pages more than in 2 hours. Which equation gives p?
- A3p + 2p = 18
- B3p = 2p + 18
- Cp = 18 × 3 × 2
- D2p = 3p + 18
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Answer: B) 3p = 2p + 18
Three hours' pages equal two hours' pages plus 18: 3p=2p+18, so p=18.