Question
A hollow cylinder has an internal radius of 7 cm and an
external radius of 10 cm. If its height is 20 cm, find the total surface area of the cylinder.Solution
The total surface area of a hollow cylinder is given by: TSA = 2πh(R + r) + 2π(R² - r²) Where h = 20 cm, R = 10 cm (external radius), r = 7 cm (internal radius). TSA = 2π(20)(10 + 7) + 2π(10² - 7²) = 2π(20)(17) + 2π(100 - 49) = 680π + 2π(51) = 680π + 102π = 782π cm² ≈ 782 × 3.14 ≈ 2455.48 cm² Correct Option: d
Person A is 80% more efficient than person B. A and B together can complete a certain task in 10 days, while B and C together can complete the same task...
A buffalo alone can plough field ‘A’ in 20 days. A Bull alone can plough the field ‘A’ in 10 days. Find the number of days taken by 1 bulls and ...
‘A’ can do a piece of work in 15 days. ‘B’ can do 60% of the same work in 20 days. If they work together for the entire time and get paid Rs.145...
 Ajay, Bablu and Chirag can complete a certain work in 21, 28 and 15 days respectively. Ajay and Chirag started the work while Bablu joined them after ...
"A certain sales target can be completed by a team of both men and womens in 60 days. If you replace eight womens with eight men, the same target can be...
Working in a shift of 5 hours 39 workers take 12 days to build a stretch of highway. In how many days will 30 workers working 6 hours a day, complete th...
P and Q can do a piece of work in 32 and 40 days respectively. They began to work together but P leaves after sometimes and Q completed remaining work i...
- Pipes A and B can fill a cistern in 48 and 80 minutes respectively. Another pipe C can empty the cistern in 1 hour 36 minutes. A and C are opened first. Af...
‘A’ and ‘B’ can do a piece of work in 12 days and 24 days, respectively. They started working together but ‘A’ left after 4 days. Find the t...
Working alone, B can complete the work in 30 days. C is twice as efficient as B and A takes 20 days more than it takes C to complete the work. Working t...
Relevant for Exams:
