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Elementary Mathematics Flashcards

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

Read the first 6 Elementary Mathematics flashcards as text

  1. Two pipes can fill a tank in 10 and 15 hours respectively. How long will they take together?

    Answer: 6 hours

    Combined rate = 1/10 + 1/15 = 3/30 + 2/30 = 5/30 = 1/6; time = 6 hours.

  2. If the ratio of two numbers is 3:5 and their sum is 96, what is the larger number?

    Answer: 60

    Larger number = (5/8) × 96 = 60.

  3. A man walks 4 km north and then 3 km east. How far is he from his starting point?

    Answer: 5 km

    Distance = √(4² + 3²) = √(16+9) = √25 = 5 km by the Pythagorean theorem.

  4. What is the compound interest on $1000 at 10% per annum for 2 years?

    Answer: $210

    CI = 1000 × (1.1)² − 1000 = 1210 − 1000 = $210.

  5. Solve: 3(2x − 4) = 18

    Answer: x = 5

    6x − 12 = 18 → 6x = 30 → x = 5.

  6. How many prime numbers lie between 1 and 20?

    Answer: 8

    The primes are 2, 3, 5, 7, 11, 13, 17, 19 — a total of 8 numbers.

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Sources & references

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  1. upsc.gov.in — Test delivery, fees, exam format, passing score, retake policy, time limit · verified Oct 2026