Question
Pipe A can fill a tank in 12 hours and pipe B can fill
it in 15 hours. A third pipe C can empty a full tank in 20 hours. If all three pipes are opened together, in how many hours will the tank be filled?Solution
Let total work = 1 tank. Rates: A: 1/12 tank/hour B: 1/15 tank/hour C: −1/20 tank/hour (emptying) Net rate = 1/12 + 1/15 − 1/20 LCM of 12, 15, 20 is 60: = (5 + 4 − 3) / 60 = 6/60 = 1/10 tank/hour Time to fill = 1 ÷ (1/10) = 10 hours
What approximate value will come in place of the question mark (?) in the following question? (Note: You are not expected to calculate the exact value.)...
20.11% of 159.99 + √99.97 ÷ 5.02 = ?
24.912% of ? – 35.06% of 199.91 = 19.97% of 224.89
45.05% of 260.05 – 20.15% of 149.99 × 3.02 = ?
83.781 `xx` 728.910 `-:` (3.008)2 = ?
Determine the simplified value of the given mathematical expression.
? = (5.8)2 + (8.9)2 + (4.7) 2 + 24.7% of 20
20.02% of (95.96 × 104.01 – 56.02 × 64.04) – ? = 12.02 × 39.96 + 103.03
19.22 × 11.99 + 142.15 = ?
(?)2 = (5.99)2 + (7.88)2 + 43.99
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