The following steps will be useful to find the least number which has to multiplied by the given number to get a perfect square. Show
1. Decompose the given numbers into its prime factors. 2. Write the prime factors as pairs such that each pair has two same prime factors. 3. Find the prime factor which does not occur in pair. That is the least number to be multiplied by the given number to get a perfect square. Example 1 : Find the least number multiplied by 200 to get a perfect square. Solution : Decompose 200 into its prime factors. Prime factors of 200 : 200 = 2 ⋅ 2 ⋅ 2 ⋅ 5 ⋅ 5 = (2 ⋅ 2) ⋅ 2 ⋅ (5 ⋅ 5) The prime factor 2 does not occur in pair. So, '2' is the least number to be multiplied by 200 to get a perfect square. Justification : √[2(200)] = √[2(2 ⋅ 2 ⋅ 2 ⋅ 5 ⋅ 5)] √400 = √[(2 ⋅ 2)(2 ⋅ 2)(5 ⋅ 5)] = 2 ⋅ 2 ⋅ 5 = 20 Further, 2(200) = 400 = 202 Example 2 : Find the least number multiplied by 252 to get a perfect square. Solution : Decompose 252 into its prime factors. Prime factors of 252 : 252 = 2 ⋅ 2 ⋅ 3 ⋅ 3 ⋅ 7 = (2 ⋅ 2) ⋅ (3 ⋅ 3) ⋅ 7 The prime factor 7 does not occur in pair. So, '7' is the least number to be multiplied by 252 to get a perfect square. Justification : √[7(252)] = √[7(2 ⋅ 2 ⋅ 3 ⋅ 3 ⋅ 7)] √1764 = √[(2 ⋅ 2)(3 ⋅ 3)(7 ⋅ 7)] = 2 ⋅ 3 ⋅ 7 = 42 Further, 7(252) = 1764 = 422 Example 3 : Find the least number multiplied by 180 to get a perfect square. Solution : Decompose 180 into its prime factors. Prime factors of 180 : 180 = 2 ⋅ 2 ⋅ 3 ⋅ 3 ⋅ 5 = (2 ⋅ 2) ⋅ (3 ⋅ 3) ⋅ 5 The prime factor 5 does not occur in pair. So, '5' is the least number to be multiplied by 180 to get a perfect square. Justification : √[5(180)] = √[5(2 ⋅ 2 ⋅ 3 ⋅ 3 ⋅ 5)] √900 = √[(2 ⋅ 2)(3 ⋅ 3)(5 ⋅ 5)] = 2 ⋅ 3 ⋅ 5 = 30 Further, 5(180) = 900 = 302 Example 4 : Find the least number multiplied by 90 to get a perfect square. Solution : Decompose 90 into its prime factors. Prime factors of 90 : 90 = 2 ⋅ 3 ⋅ 3 ⋅ 5 = 2 ⋅ (3 ⋅ 3) ⋅ 5 The prime factors 2 and 5 do not occur in pair. Product of 2 and 5 : 2 ⋅ 5 = 10 So, '10' is the least number to be multiplied by 90 to get a perfect square. Justification : √[10(90)] = √[10(2 ⋅ 3 ⋅ 3 ⋅ 5)] √900 = √[(2 ⋅ 5)(2 ⋅ 3 ⋅ 3 ⋅ 5)] = √[(2 ⋅ 2)(3 ⋅ 3)(5 ⋅ 5)] = 2 ⋅ 3 ⋅ 5 = 30 Further, 10(90) = 900 = 302 Example 5 : Find the least number multiplied by 120 to get a perfect square. Solution : Decompose 120 into its prime factors. Prime factors of 120 : 120 = 2 ⋅ 2 ⋅ 2 ⋅ 3 ⋅ 5 = (2 ⋅ 2) ⋅ 2 ⋅ 3 ⋅ 5 The prime factors 2, 3 and 5 do not occur in pair. Product of 2, 3 and 5 : 2 ⋅ 3 ⋅ 5 = 30 So, '30' is the least number to be multiplied by 120 to get a perfect square. Justification : √[30(120)] = √[30(2 ⋅ 2 ⋅ 2 ⋅ 3 ⋅ 5)] √3600 = √[(2 ⋅ 3 ⋅ 5)(2 ⋅ 2 ⋅ 2 ⋅ 3 ⋅ 5)] = √[(2 ⋅ 2)(2 ⋅ 2)(3 ⋅ 3)(5 ⋅ 5)] = 2 ⋅ 2 ⋅ 3 ⋅ 5 = 60 Further, 30(120) = 3600 = 602 Kindly mail your feedback to We always appreciate your feedback. ©All rights reserved. onlinemath4all.com
The question is about perfect square factors. A number is given as multiplication of prime factors. We need to find out the number of perfect square factors of that number. Dealing with factors of a number is a vital component in CAT Number Systems: Factors. A range of CAT questions can be asked based on this simple concept of Factors. CAT exam has always tested the idea of Factors from Number systems. The idea of Factors questions forms an integral part of the CAT syllabus. Question 3: How many factors of 25 * 36 * 52 are perfect squares? Best CAT Online Coaching Try upto 40 hours for free Learn from the best!2IIM : Best Online CAT Coaching.Best CAT Coaching in ChennaiCAT Coaching in Chennai - CAT 2022 |