Q: A man is 3 years older than his wife and four times as old as his son. If the son becomes 15 years old after 3 years. Then what is the present age of the wife?
Solution: 45 years
Q: If N is the greatest number that will divide 1305, 4665 and 6905, leaving the same remainder in each case. What is the sum of the digits of N ?
Solution: N = H.C.F. of (4665 - 1305), (6905 - 4665) and (6905 - 1305) = H.C.F. of 3360, 2240 and 5600 = 1120. Sum of digits in N = ( 1 + 1 + 2 + 0 ) = 4
Q: H.C.F of 4 x 27 x 3125, 8 x 9 x 25 x 7 and 16 x 81 x 5 x 11 x 49 is :
Solution: 4 x 27 x 3125 = 22 × 33 × 55 ; 8 x 9 x 25 x 7 = 23 × 32 × 52 × 7 16 x 81 x 5 x 11 x 49 = 24 × 34 × 5 × 11 × 72 H.C.F = 22 × 32 × 5 = 180.
Q: A student can divide her books into groups of 5, 9 and 13. what is the smallest possible number of the books ?
Solution: The smallest possible number of books = L.C.M of 5, 9 and 13.Therefore, L.C.M of 5,9 and 13 is = 5 x 9 x 13 = 585.
Q: If the sum of two numbers is 55 and the H.C.F. and L.C.M. of these numbers are 5 and 120 respectively, then the sum of the reciprocals of the numbers is equal to ?
Solution: Let the numbers be a and b.We know that product of two numbers = Product of their HCF and LCMThen, a + b = 55 and ab = 5 x 120 = 600.=> The required sum = (1/a) + (1/b) = (a+b)/ab=55/600 = 11/120
Q: 10 years ago, the average age of a family of 4 members was 24 years. Two children having been born (with age diference of 2 years), the present average age of the family is the same. The present age of the youngest child is :
Solution: Total age of 4 members, 10 years ago = (24 x 4) years = 96 years. Total age of 4 members now = [96 + (10 x 4)] years = 136 years. Total age of 6 members now = (24 x 6) years = 144 years. Sum of the ages of 2 children = (144 - 136) years = 8 years. Let the age of the younger child be x years. Then, age of the elder child = (x+2) years. So, x+(x+2) =8 <=> x=3 Age of younger child = 3 years.
Q: Vinod have 20 rupees. He bought 1, 2, 5 rupee stamps. They are different in numbers by the reason of no change, the shop keeper gives 3 one rupee stamps. So how many stamps Vinod have ?
Solution: Given total rupees = 20 RsNo. of one rupee stamps = 3Now, remaining money = Rs. 17With that he buys only 2 and 5 rupee stampsLet number of Rs. 5 stamps = KLet number of Rs. 2 stamps = L5K + 2L = 17K = 3, L = 1 (possible)L = 6, K = 1 (possible)=> But given that they are different in number so, K is not equal to 3one rupee stamps = 32 two stamps = 65 rupee stamps = 1Total number of stamps = 10.
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