EXERCISE 3A(1) Using the prime factorization method, find which of the following numbers are perfect squares: (i) 441 = 3 × 3 × 7 × 7 = 32 × 72 (ii) 576 = 2 × 2 × 2 × 2 × 2 × 2 × 3 × 3 = 26 × 32 (iii) 11025 = 5 × 5 × 3 × 3 × 7 × 7 = 52 × 32 × 72 (iv) 1176 = 2 × 2 × 2 × 3 × 7 × 7 (v) 5625 = 3 × 3 × 5 × 5 × 5 × 5 = 32 × 54 (vi) 9075 = 3 × 5 × 5 × 11 × 11 (vii) 4225 = 5 × 5 × 13 × 13 = 52 × 132 (viii) 1089 = 3 × 3 × 11 × 11 = 32 × 112 (2) Show that each of the following numbers is a perfect square. In each case, find the number whose square is the given number: (i) 1225 = 5 × 5 × 7 × 7 = 52 × 72 Thus, 1225 is the product of pairs of equal factors. ∴ 1225 is a perfect square. Also = (5 × 7)2 = (35)2 Hence, 35 is the number whose square is 1225. (ii) 2601 = 3 × 3 × 17 × 17 = 32 × 172 Thus, 2601 is the product of pairs of equal factors. ∴ 2601 is a perfect square. Also = (3 × 17)2 = (51)2 Hence, 51 is the number whose square is 2601. (iii) 5929 = 7 × 7 × 11 × 11 = 72 × 112 Thus, 5929 is the product of pairs of equal factors. ∴ 5929 is a perfect square. Also = (7 × 11)2 = (77)2 Hence, 77 is the number whose square is 5929. (iv) 7056 = 2 × 2 × 2 × 2 × 3 × 3 × 7 × 7 = 22 × 22 × 32 × 72 Thus, 7056 is the product of pairs of equal factors. ∴ 7056 is a perfect square. Also = (2 × 2 × 3 × 7)2 = (84)2 Hence, 84 is the number whose square is 7056. (v) 8281 = 7 × 7 × 13 × 13 = 72 × 132 Thus, 8281 is the product of pairs of equal factors. ∴ 8281 is a perfect square. Also = (7 × 13)2 = (91)2 Hence, 91 is the number whose square is 8281. (3) By what least number should the given number be multiplied to get a perfect square number? In each case, find the number whose square is the new number. (i) 3675 Solution: Resolving 3675 into prime factors, we get 3675 = 3 × 5 × 5 × 7 × 7 = (3 × 52 × 72) Thus, to get a perfect square number, the given number should be multiplied by 3. New number = (32 × 52 × 72) = (3 × 5 × 7)2 = (105)2 Hence, the number whose square is the new number = 105. (ii) 2156 Solution: Resolving 2156 into prime factors, we get 2156 = 2 × 2 × 7 × 7 × 11 Thus, to get a perfect square number, the given number should be multiplied by 11. New number = (22 × 72 × 112) = (2 × 7 × 11)2 = (154)2 Hence, the number whose square is the new number = 154. (iii) 3332 Solution: Resolving 3332 into prime factors, we get 3332 = 2 × 2 × 7 × 7 × 17 Thus, to get a perfect square number, the given number should be multiplied by 17. New number = (22 × 72 × 172) = (2 × 7 × 17)2 = (238)2 Hence, the number whose square is the new number = 238. (iv) 2925 Solution: Resolving 2925 into prime factors, we get 2925 = 3 × 3 × 5 × 5 × 13 Thus, to get a perfect square number, the given number should be multiplied by 13. New number = (32 × 52 × 132) = (3 × 5 × 13)2 = (195)2 Hence, the number whose square is the new number = 195. (v) 9075 Solution: Resolving 9075 into prime factors, we get 9075 = 3 × 5 × 5 × 11 × 11 Thus, to get a perfect square number, the given number should be multiplied by 3. New number = (32 × 52 × 112) = (3 × 5 × 11)2 = (165)2 Hence, the number whose square is the new number = 165. (vi) 7623 Solution: Resolving 7623 into prime factors, we get 7623 = 3 × 3 × 7 × 11 × 11 Thus, to get a perfect square number, the given number should be multiplied by 7. New number = (32 × 72 × 112) = (3 × 7 × 11)2 = (231)2 Hence, the number whose square is the new number = 231. (vii) 3380 Solution: Resolving 3380 into prime factors, we get 3380 = 2 × 2 × 5 × 13 × 13 Thus, to get a perfect square number, the given number should be multiplied by 5. New number = (22 × 52 × 132) = (2 × 5 × 13)2 = (130)2 Hence, the number whose square is the new number = 130. (viii) 2475 Solution: Resolving 2475 into prime factors, we get 2475 = 3 × 3 × 5 × 5 × 11 Thus, to get a perfect square number, the given number should be multiplied by 11. New number = (32 × 52 × 112) = (3 × 5 × 11)2 = (165)2 Hence, the number whose square is the new number = 165. (4) By what least number should the given number be divided to get a perfect square number? In each case, find the number whose square is the new number. (i) 1575 Solution: Resolving 1575 into prime factors, we get 1575 = 3 × 3 × 5 × 5 × 7 = (32 × 52 × 7) Thus, to get a perfect square number, the given number should be divided by 7. New number obtained = (32 × 52) = (3 × 5)2 = (15)2 Hence, the number whose square is the new number = 15. (ii) 9075 Solution: Resolving 9075 into prime factors, we get 9075 = 3 × 5 × 5 × 11 × 11 = (3 × 52 × 112) Thus, to get a perfect square number, the given number should be divided by 3. New number obtained = (52 × 112) = (5 × 11)2 = (55)2 Hence, the number whose square is the new number = 55. (iii) 4851 Solution: Resolving 4851 into prime factors, we get 4851 = 3 × 3 × 7 × 7 × 11 = (32 × 72 × 11) Thus, to get a perfect square number, the given number should be divided by 11. New number obtained = (32 × 72) = (3 × 7)2 = (21)2 Hence, the number whose square is the new number = 21. (iv) 3380 Solution: Resolving 3380 into prime factors, we get 3380 = 2 × 2 × 5 × 13 × 13 = (22 × 5 × 132) Thus, to get a perfect square number, the given number should be divided by 5. New number obtained = (22 × 132) = (2 × 13)2 = (26)2 Hence, the number whose square is the new number = 26. (v) 4500 Solution: Resolving 4500 into prime factors, we get 4500 = 2 × 2 × 3 × 3 × 5 × 5 × 5 = (22 × 32 × 5 × 52) Thus, to get a perfect square number, the given number should be divided by 5. New number obtained = (22 × 32 × 52) = (2 × 3 × 5)2 = (30)2 Hence, the number whose square is the new number = 30. (vi) 7776 Solution: Resolving 7776 into prime factors, we get 7776 = 2 × 2 × 2 × 2 × 2 × 3 × 3 × 3 × 3 × 3 = (22 × 22 × 2 × 3 × 32 × 32) Thus, to get a perfect square number, the given number should be divided by 2 × 3. New number obtained = (22 × 22 × 32 × 32) = (2 × 2 × 3 × 3)2 = (36)2 Hence, the number whose square is the new number = 36. (vii) 8820 Solution: Resolving 8820 into prime factors, we get 8820 = 2 × 2 × 3 × 3 × 5 × 7 × 7 = (22 × 32 × 5 × 72) Thus, to get a perfect square number, the given number should be divided by 5. New number obtained = (22 × 32 × 72) = (2 × 3 × 7)2 = (42)2 Hence, the number whose square is the new number = 42. (viii) 4056 Solution: Resolving 4056 into prime factors, we get 4500 = 2 × 2 × 2 × 3 × 13 × 13 = (22 × 2 × 3 × 132) Thus, to get a perfect square number, the given number should be divided by 2 × 3. New number obtained = (22 × 132) = (2 × 13)2 = (26)2 Hence, the number whose square is the new number = 26. (5) Find the largest number of 2 digits which is a perfect square. Ans: The largest 2 digits number is 99. Square of 10 = 100 > 99, thus the number would be less than 10. And the largest whole number less than 10 is 9. Therefore, 9 × 9 = 81 (6) Find the largest number of 3 digits which is a perfect square. Ans: The largest three digits number is 999. But 961 is a largest three digits number, is a perfect square. 961 = 31 × 31 Here, for easy to understand we take the before and after number of 31. Those are 30 and 32 respectively. Now, 30 × 30 = 900 and 32 × 32 = 1024. Hence, we can write 961 is largest three numbers has a perfect square. For more exercise solution, Click below – |