High School

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Q18. The ratio of P: Q= 4:3, Q:R=5:6, R:S=9:8 and T: S=10:11. What is the value of P: Q: R:S:T?
Ops: A. None of the mentioned options
B. 220: 198: 165: 175: 150
C. 220: 165: 198: 176: 160
D. 210: 150: 176: 198: 160

Q19. In how many ways can the letters M, P, T, S, X, Z, F and E be arranged together so that E and F are always together?
Ops: A. 10080
B. 2880
C. 5040
D. 40320

Q20. A cyclist rides at a speed of x km/h. Against a 5 km/h headwind, it covers 10 km in 30 minutes. Returning with the wind, he takes 20 minutes to cover 10 km. Find the cyclist's actual speed without wind.
Ops: A. 29.18 km/h
B. 26.18 km/h
C. 19.5 km/h
D. 25 km/h

Answer :

Let's tackle each question one at a time.

Q18: Finding the ratio P:Q:R:S:T

Given ratios:

  • [tex]P:Q = 4:3[/tex]
  • [tex]Q:R = 5:6[/tex]
  • [tex]R:S = 9:8[/tex]
  • [tex]T:S = 10:11[/tex]

We want to find a common ratio [tex]P:Q:R:S:T[/tex].

Step-by-step to find the ratios:

  1. For [tex]P:Q = 4:3[/tex], we can set [tex]P = 4k[/tex] and [tex]Q = 3k[/tex].

  2. For [tex]Q:R = 5:6[/tex], since [tex]Q = 3k[/tex], then [tex]R = \frac{6}{5} \times 3k = 3.6k[/tex].

  3. For [tex]R:S = 9:8[/tex], [tex]S = \frac{8}{9} \times 3.6k = 3.2k[/tex].

  4. For [tex]T:S = 10:11[/tex], [tex]T = \frac{10}{11} \times 3.2k = 2.909k[/tex].

Converting ratios to integers:
To find the smallest integer ratio, multiply through by the least common multiple of the denominators:

  • Multiply all by 55 to clear out the fractions and to bring these to whole numbers:

[tex]P = 4k \times 55 = 220,
Q = 3k \times 55 = 165,
R = 3.6k \times 55 = 198,
S = 3.2k \times 55 = 176,
T = 2.909k \times 55 = 160[/tex]

Therefore, the ratio [tex]P:Q:R:S:T[/tex] is 220:165:198:176:160.

The correct option is C.

Q19: Arranging letters M, P, T, S, X, Z, F, E with E and F together

Treat E and F as a single unit (or block), so now you are arranging 7 units: M, P, T, S, X, Z, and (EF).

  1. The 7 units can be arranged in [tex]7![/tex] ways.

    [tex]7! = 5040[/tex] ways

  2. Within the block EF, E and F can be arranged in [tex]2![/tex] ways.

Thus, total ways = [tex]7! \times 2! = 5040 \times 2 = 10080[/tex].

The correct option is A.

Q20: Finding the cyclist's actual speed without wind

The cyclist covers 10 km in 30 minutes against the wind.

The effective speed against the wind = [tex]x - 5[/tex] km/h

10 km in 0.5 hours implies [tex]x - 5 = \frac{10}{0.5} = 20[/tex]

Thus, [tex]x = 25[/tex] km/h

The correct option is D.

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