1. The least number which when divided by 6, 9, 12, 15, 18 leaves the same remainder 2 in each case, is:
A. 176
B. 178
C. 180
D. 182
Answer: Option D
Explanation:
Given numbers are: 6, 9, 12, 15, 18
LCM of given numbers = 180
So, 180 + 2 = 182 is the number that leaves 2 as a remainder.
2. The HCF of two numbers is 98 and their LCM is 2352. The sum of the numbers may be
A. 1078
B. 1398
C. 1426
D. 1484
Answer: Option A
Explanation:
Let two numbers are 98x and 98y. Then,
Product of number = Product of HCF and LCM
98x × 98y = 98 × 2352
xy = 24
Let x = 8 and y = 3 (As Co-prime factors of 24 be 8 and 3)
Then, Sum of number = 98 × 8 + 98 × 3 = 98 (11) = 1078
3. The product of HCF and LCM of 18 and 15 is
A. 120
B. 150
C. 175
D. 270
Answer: Option D
Explanation:
HCF of 18 and 15 = 3
LCM of 18 and 15 = 90
∴ Product of HCF and LCM of both numbers = 3 × 90 = 270.
4. Three planets revolve around the Sun once in 200, 250 and 300 days, respectively in their own orbits. When do they all come relatively to the same position as at a certain point of time in their orbits?
A. After 3000 days
B. After 2000 days
C. After 1500 days
D. After 1200 days
Answer: Option A
Explanation:
Given that, three planets revolve the Sun once in 200, 250 and 300 days, respectively in their own orbits.
∴ Required time = LCM of (200, 250 and 300) = 3000 days
Hence, after 3000 days they all come relatively to the same position as at a certain point of time in their orbits.
5. Find the H.C.F. and L.C.M. of 0.63, 1.05 and 2.1.
A. 0.21 and 6.30
B. 1.05 and 6.30
C. 2.1 and 0.63
D. 0.63 and 1.05
Answer: Option A
Explanation:
Making the same number of decimal places, the given numbers are 0.63, 1.05 and 2.10.
Without decimal places, these numbers are 63, 105 and 210.
Now, H.C.F of 63, 105 and 210 is 21.
∴ H.C.F, of 0.63, 1.05 and 2.1 is 0.21.
L.C.M. 63, 105 and 210 is 630
∴ L.C.M. of 0.63, 1.05 and 2.1 is 6.30.