Questions & Answers: "Factors and Multiples (HCF and LCM)"

Complete guide to "Factors and Multiples (HCF and LCM)" for Math students. Below you will find important questions and model answers to help you prepare.

7 Questions

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Question 1

1 Mark

If L.C.M. of two consecutive even numbers is 312, then what will be the sum of these two numbers?

Options

Option A

48

Option B

46

Option C

52

Option D is correct

50

Question 2

1 Mark

Reena had some flowers. She prepared garlands from them. When she made every garland of 12 flowers, she was left with 11 flowers. If she had used 16 flowers for each garland then she would have left with 15 flowers. If she had used 18 flowers for each garland then she would have left with 17 flowers. Find the minimum number of flowers that she may have.

Options

Option A

161

Option B

155

Option C is correct

143

Option D

145

Question 3

1 Mark

Find the smallest number from the following such that when it is divided by every 1 digit prime number, every time the remainder is 1.

Options

Option A

106

Option B is correct

211

Option C

31

Option D

71

Question 4

1 Mark

If a number is divided by 18 then the remainder is 1, if it is divided by 24 then the remainder is 7 and if it is divided by 36 then the remainder is 19. What is the smallest such type of number?

Options

Option A

91

Option B

71

Option C

79

Option D is correct

55

Question 5

1 Mark

The LCM of two co-prime numbers is 910 and their sum is 83. What will be the difference between the two numbers?

Options

Option A is correct

57

Option B

60

Option C

81

Option D

75

Question 6

1 Mark

H.C.F of two digit two numbers is 14 and L.C.M. is 490. Find the sum of those two numbers.

Options

Option A

140

Option B

147

Option C is correct

168

Option D

182

Question 7

1 Mark

L.C.M. of two consecutive odd numbers is 8463. Find the bigger odd number out of the two numbers.

Options

Option A

91

Option B is correct

93

Option C

95

Option D

97

Explanation

Let the two consecutive odd numbers be nn and n+2n+2. Consecutive odd numbers are always coprime, meaning their greatest common divisor (HCF) is 11. For coprime numbers, their Least Common Multiple (LCM) is equal to their product. Given that the LCM is 84638463, we have n(n+2)=8463n(n+2) = 8463. This is a quadratic equation n2+2n8463=0n^2 + 2n - 8463 = 0. We can estimate nn by taking the square root of 84638463. 846391.99\sqrt{8463} \approx 91.99. Since the numbers are consecutive odd integers, they must be close to 91.9991.99. The two odd integers closest to 91.9991.99 with a difference of 22 are 9191 and 9393. Let's verify: 91×93=(921)(92+1)=92212=84641=846391 \times 93 = (92-1)(92+1) = 92^2 - 1^2 = 8464 - 1 = 8463. Thus, the two numbers are 9191 and 9393. The bigger odd number is 9393.