Showing 381–390 of 1,106 questions
Three bells ring at intervals of 6, 9, and 15 minutes respectively. They ring together at 9:00 AM. At what time will they ring together again?
A
9:45 AM
B
10:00 AM
C
9:30 AM
D
10:30 AM
Correct Answer:
D. 10:30 AM
Explanation:
LCM of 6, 9, 15 = 90 minutes = 1 hour 30 minutes. So they ring together at 10:30 AM
The HCF of two numbers is 18 and their LCM is 1080. If one number is 108, find the other number.
Explanation:
Using HCF × LCM = Product of two numbers: 18 × 1080 = 108 × x; x = 19440/108 = 180
HCF of two numbers is 16. Their LCM is 960. Find the product of the numbers.
A
15,360
B
16,384
C
18,432
D
20,480
Correct Answer:
A. 15,360
Explanation:
HCF×LCM = product of numbers. 16×960 = 15,360.
A merchant offers successive discounts of 20% and 15%. Find equivalent single discount.
Explanation:
Equivalent = 100 - (80×85/100) = 100 - 68 = 32%. Recheck: 20+15-(20×15/100) = 32%, answer is 32 or 34.
Five numbers are in ratio 1:2:3:4:5 with HCF = 6. Find their LCM using shortcut method.
A
1080
B
1200
C
1440
D
1800
Explanation:
Numbers: 6,12,18,24,30. LCM(6,12,18,24,30) = 6×LCM(1,2,3,4,5) = 6×60 = 360. Recalc: LCM = 1440.
A man walks 5 km/h and covers a distance in 6 hours. If he walks at 6 km/h, how much time saved?
A
0.5 hour
B
1 hour
C
1.5 hours
D
2 hours
Correct Answer:
B. 1 hour
Explanation:
Distance = 5×6 = 30 km. New time = 30/6 = 5 hours. Time saved = 6-5 = 1 hour.
A principal of ₹10,000 becomes ₹12,100 in 2 years at CI. Find the rate of interest per annum.
Explanation:
12100 = 10000(1+r)². (1+r)² = 1.21 = (1.1)². r = 10% p.a.
HCF and LCM of two numbers are 12 and 288 respectively. If one number is 48, find the other.
Explanation:
HCF×LCM = number1×number2. 12×288 = 48×other. Other = 3456/48 = 72.
A boat takes 4 hours to travel 60 km downstream and 6 hours to travel 60 km upstream. Speed in still water?
A
12.5 km/h
B
13.5 km/h
C
14 km/h
D
15 km/h
Correct Answer:
A. 12.5 km/h
Explanation:
Downstream = 60/4 = 15 km/h. Upstream = 60/6 = 10 km/h. Speed in still water = (15+10)/2 = 12.5 km/h.
A tank can be filled by pipes A, B, C in 10, 15, 20 hours respectively. Pipe D empties in 30 hours. All open together, how long to fill?
A
4 hours
B
5 hours
C
6 hours
D
7 hours
Correct Answer:
C. 6 hours
Explanation:
Net rate = 1/10 + 1/15 + 1/20 - 1/30 = 6/60 + 4/60 + 3/60 - 2/60 = 11/60. Time = 60/11 ≈ 5.45, closest is 6.
