Q.12 The ratio of height of a right cylinder to its radius is 1:2 and it's
curved surface area is 616 m? Find it's diameter ?
Answers
Answer:
The word “hundred” comes from the old Norse term, “hundrath”, which actually means 120 and not 100.
2. In a room of 23 people there’s a 50% chance that two people have the same birthday.
Illustration of birthday cake
3. Most mathematical symbols weren’t invented until the 16th century. Before that, equations were written in words.
4. “Forty” is the only number that is spelt with letters arranged in alphabetical order.
speed limit 40 sign
5. Conversely, “one” is the only number that is spelt with letters arranged in descending order.
6. From 0 to 1000, the only number that has the letter “a” in it is “one thousand”.
7. ‘Four’ is the only number in the English language that is spelt with the same number of letters as the number itself.
8. Every odd number has an “e” in it.
9. The reason Americans call mathematics “math”, is because they argue that “mathematics” functions as a singular noun so ‘math’ should be singular too.
10. Markings on animal bones indicate that humans have been doing maths since around 30,000BC.
11. “Eleven plus two” is an anagram of “twelve plus one” which is pretty fitting as the answer to both equations is 13.
12. Also, there are 13 letters in both “eleven plus two” and “twelve plus one”.
13. Zero is not represented in Roman numerals.
14. The word “mathematics” only appears in one Shakespearean play, “The Taming of the Shrew”.
portrait of Shakespeare
15. -40 °C is equal to -40 °F.
16. In France, a pie chart is sometimes referred to as a “camembert”.
17. The symbol for division (i.e.÷) is called an obelus.
18. 2 and 5 are the only prime numbers that end in 2 or 5.
19. A ‘jiffy’ is an actual unit of time. It means 1/100th of a second.
20. If you shuffle a deck of cards properly, it’s more than likely that the exact order of the cards you get has never been seen before in the whole history of the universe.
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9th
Maths
Surface Areas and Volumes
Volume of Cube, Cuboid and Cylinder
The ratio between the curve...
Maths
The ratio between the curved surface area and the total surface area of a right circular cylinder is 1:2. Find the volume of the cylinder if its total surface area is 616 cm sq.
Medium
Answer
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Given that:Curved surface area : Total surface area =1:2
Curved surface area :616=1:2
Curved surface area=
2
616
=308
⇒
2πr(h+r)
2πrh
=
2
1
⇒
h+r
h
=
2
1
⇒2h=h+r
⇒h=r
Curved Surface area=2πrh=2πr
2
=308 since h=r
⇒2×
7
22
r
2
=308
⇒r
2
=
44
308×7
=49
⇒r=7cm
Since r=h
h=7cm
Volume of the cylinder=πr
2
h=
7
22
×7×7×7=1078cm
3
∴ Volume of the cylinder is 1078 cu cm.