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Arithmetic and Number Systems Flashcards

6 cards from real RRB NTPC practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

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  1. A shopkeeper marks his goods 25% above cost price and gives a 10% discount. What is his profit percentage?

    Answer: 12.5%

    Let CP = 100. MP = 125. SP = 125 × 0.9 = 112.5. Profit% = (112.5-100)/100 × 100 = 12.5%.

  2. Find the value of: √(0.0081)

    Answer: 0.09

    √(0.0081) = √(81/10000) = √81/√10000 = 9/100 = 0.09.

  3. A boat travels 30 km upstream in 6 hours and 30 km downstream in 3 hours. What is the speed of the stream?

    Answer: 2.5 km/h

    Upstream speed = 30/6 = 5 km/h; Downstream speed = 30/3 = 10 km/h. Stream speed = (Downstream - Upstream)/2 = (10-5)/2 = 2.5 km/h.

  4. The difference between a two-digit number and the number obtained by interchanging its digits is 36. What is the difference between the digits?

    Answer: 4

    Let digits be a and b. Original number = 10a+b, reversed = 10b+a. Difference: (10a+b)-(10b+a) = 9(a-b) = 36 → a-b = 4.

  5. If A can do a piece of work in 10 days and B can do the same work in 15 days, how many days will they take together?

    Answer: 6 days

    A's work per day = 1/10; B's work per day = 1/15. Together = 1/10 + 1/15 = 3/30 + 2/30 = 5/30 = 1/6. So they finish in 6 days.

  6. What is the compound interest on Rs. 10,000 at 10% per annum for 2 years?

    Answer: Rs. 2,100

    CI = P[(1+r/100)^n - 1] = 10000[(1.1)² - 1] = 10000[1.21 - 1] = 10000 × 0.21 = Rs. 2,100.

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