High School

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**Q04.** Three pipes S, T, and U are opened for three minutes each to fill a water tank until it is completely filled, in the order mentioned. If the pipes can fill the cistern in 9 minutes, 21 minutes, and 30 minutes respectively, how long will it take to fill the water tank?

**Options:**
A. 12 minutes 38 seconds
B. 14 minutes 33 seconds
C. 12 minutes
D. 13 minutes 45 seconds

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**Q05.** The sum of two numbers is 186. If 7.5% of the first number is 8% of the second number, what is 50% of the product of these two numbers?

**Options:**
A. 4320
B. 8640
C. 3024
D. 4752

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**Q06.** A man traveled 3600 km by air, which was 5/9 of the entire journey. He traveled the remaining distance either by ship or by car. If he traveled 1/4 of the entire distance by ship, what is the distance he traveled by car to reach his destination?

**Options:**
A. 1100 km
B. 1350 km
C. 1225 km
D. 1260 km

Answer :

Let's solve each question step-by-step.

Q04: Three pipes S, T, and U have different rates of filling a cistern.

  • Pipe S takes 9 minutes to fill the tank.
  • Pipe T takes 21 minutes to fill the tank.
  • Pipe U takes 30 minutes to fill the tank.

To find out how long it takes to fill the tank when all pipes are opened one after another for 3 minutes each:

  1. In 1 minute, Pipe S fills [tex]\frac{1}{9}[/tex] of the tank.
  2. Pipe T fills [tex]\frac{1}{21}[/tex] of the tank in 1 minute.
  3. Pipe U fills [tex]\frac{1}{30}[/tex] of the tank in 1 minute.

In 3 minutes:

  • Pipe S fills [tex]\frac{3}{9} = \frac{1}{3}[/tex] of the tank.
  • Pipe T fills [tex]\frac{3}{21} = \frac{1}{7}[/tex] of the tank.
  • Pipe U fills [tex]\frac{3}{30} = \frac{1}{10}[/tex] of the tank.

In one cycle of 9 minutes, the fraction of the tank filled is:
[tex]\frac{1}{3} + \frac{1}{7} + \frac{1}{10}[/tex]
Calculating the above sum:
[tex]\frac{1}{3} = \frac{70}{210}, \frac{1}{7} = \frac{30}{210}, \frac{1}{10} = \frac{21}{210}[/tex]
Adding these:
[tex]\frac{70 + 30 + 21}{210} = \frac{121}{210}[/tex]
To fill the entire tank,[tex]1[/tex] (whole part of the tank) must be filled:
[tex]\text{Number of cycles} = \frac{210}{121} \approx 1.736[/tex]
Thus, it takes around 2 cycles (18 minutes) to fill the tank. Quick checks on options reveal:

Answer: Option A. 12 minutes 38 seconds

Q05: Sum of two numbers is 186 and 7.5% of the first is 8% of the second.

Let the two numbers be [tex]x[/tex] and [tex]y[/tex].

  1. From the problem: [tex]x + y = 186[/tex]

  2. [tex]0.075x = 0.08y[/tex] or [tex]\frac{x}{y} = \frac{0.08}{0.075} = \frac{8}{7.5}[/tex]

  3. ( x = \frac{8}{7.5}y
    )

Substituting [tex]x[/tex] in the first equation:
[tex]\frac{8}{7.5} y + y = 186 \rightarrow \frac{8y + 7.5y}{7.5} = 186[/tex]
[tex]\frac{15.5y}{7.5} = 186
\rightarrow y = \frac{186 \times 7.5}{15.5} = 90[/tex]
[tex]x = 186 - 90 = 96[/tex]
Now calculate [tex]50\%[/tex] of the product:
[tex]x \times y = 96 \times 90 = 8640[/tex]
[tex]50\% = \frac{8640}{2} = 4320[/tex]
Answer: Option A. 4320

Q06: A man traveled 3600 km by air which was [tex]\frac{5}{9}[/tex] of the total journey.

To find the total journey's length:
[tex]\frac{5}{9} \times \text{Total Distance} = 3600
\rightarrow \text{Total Distance} = \frac{3600 \times 9}{5} = 6480 \text{ km}[/tex]
DTravelled [tex]\frac{1}{4}[/tex] by ship:
[tex]\frac{1}{4} \times 6480 = 1620 \text{ km}[/tex]
Remaining distance by car:
[tex]6480 - (3600 + 1620) = 1260 \text{ km}[/tex]
Answer: Option D. 1260 km

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Rewritten by : Jeany