UPSC Prelims 2016 · CSAT
Question 14: Basic Numeracy
There are some nectar-filled flowers on a tree and some bees are hovering on it. If one bee lands on each flower, one bee will be left out. If two bees land on each flower, one flower will be left out. The number of flowers and bees respectively are :
AnswerUPSC’s answer is (c).
Let flowers be f and bees be b. One bee per flower leaves one bee out: b = f + 1. Two bees per flower leaves one flower empty: b = 2(f - 1). Equate: f + 1 = 2f - 2, so f = 3 and b = 4. Check: 3 flowers take 3 bees with 1 bee left over; with two per flower, 4 bees fill 2 flowers and 1 flower stays empty. Tip: when options are small numbers, test them against both conditions.
Why each option is right or wrong
- (a) 2 flowers and 4 bees: one per flower leaves 2 bees out, not 1.
- (b) 3 flowers and 2 bees: there are fewer bees than flowers.
- (c) Right: 3 flowers and 4 bees satisfy both conditions.
- (d) 4 flowers and 3 bees: there are fewer bees than flowers.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2016, General Studies Paper II (CSAT), Series A. The paper on upsc.gov.in.