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Home›UPSC Prelims›Paper 2: General Studies II (CSAT)›Civil Services Aptitude Test (CSAT)›Basic Numeracy & Data Interpretation›How many zeroes are there at the end of the following product? 1 × 5

How many zeroes are there at the end of the following product?
1 × 5 × 10 × 15 × 20 × 25 × 30 × 35 × 40 × 45 × 50 × 55 × 60

20203Mprelimsupscyear-2020p2quantitative-aptitude
A.(a) 10Correct
B.(b) 12
C.(c) 14
D.(d) 15
Explanation & Solution

Correct Answer: (A) 10

The number of trailing zeroes is determined by min⁡(v2,v5)\min(v_2, v_5)min(v2​,v5​). Counting the factors of 2 in the even multiples: 10(21),20(22),30(21),40(23),50(21),60(22)10(2^1), 20(2^2), 30(2^1), 40(2^3), 50(2^1), 60(2^2)10(21),20(22),30(21),40(23),50(21),60(22), giving 1+2+1+3+1+2=101 + 2 + 1 + 3 + 1 + 2 = 101+2+1+3+1+2=10 factors of 2. Although there are 14 factors of 5, the total number of complete pairs of (2×5)(2 ×\times× 5)(2×5) is limited to 10, producing exactly 10 trailing zeroes.

हिंदी में प्रश्न एवं आदर्श उत्तर

गुणनफल 1 × 5 × 10 × 15 × 20 × 25 × 30 × 35 × 40 × 45 × 50 × 55 × 60 के अंत में कितने शून्य होंगे?

A.(a) 10सही
B.(b) 12
C.(c) 14
D.(d) 15

सही उत्तर: (A) 10

शून्यों की संख्या min⁡(v2,v5)\min(v_2, v_5)min(v2​,v5​) से निर्धारित होती है। गुणनफल में 2 के गुणनखंड केवल सम संख्याओं में हैं: 10(21),20(22),30(21),40(23),50(21),60(22)10(2^1), 20(2^2), 30(2^1), 40(2^3), 50(2^1), 60(2^2)10(21),20(22),30(21),40(23),50(21),60(22), जिनका योग 1+2+1+3+1+2=101 + 2 + 1 + 3 + 1 + 2 = 101+2+1+3+1+2=10 है। चूँकि 5 के गुणनखंड 14 हैं, अतः केवल 10 शून्य ही बन सकते हैं।

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