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# A bicycle tire has a diameter of 70 centimeters. Approximately how man

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A bicycle tire has a diameter of 70 centimeters. Approximately how man  [#permalink]

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11 Apr 2018, 20:20
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A bicycle tire has a diameter of 70 centimeters. Approximately how many revolutions does the tire make if the bicycle travels 1 kilometer. (1 kilometer = 1,000 meters = 100,000 centimeters)

A. 150
B. 450
C. 900
D. 1500
E. 2200

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Re: A bicycle tire has a diameter of 70 centimeters. Approximately how man  [#permalink]

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11 Apr 2018, 20:22
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Re: A bicycle tire has a diameter of 70 centimeters. Approximately how man  [#permalink]

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11 Apr 2018, 23:40
Diameter = 70 cm, hence radius =35cm. In one revolution the tire will cover the length equivalent to it's perimeter which is equals 2*π*35 cm. So to cover 1km or 100000 cm the cycle will have to move = n*2*π*35 cm
>> n = 100000*7/(2*22*35) = 5000/11 = 450 approx. Hence, option B. 450
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Re: A bicycle tire has a diameter of 70 centimeters. Approximately how man  [#permalink]

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12 Apr 2018, 06:46
Bunuel wrote:
A bicycle tire has a diameter of 70 centimeters. Approximately how many revolutions does the tire make if the bicycle travels 1 kilometer. (1 kilometer = 100 meters = 100000 centimeters)

A. 150
B. 450
C. 900
D. 1500
E. 2200

(circumference)*(# of revolutions) = Distance, so

Number of revolutions =$$\frac{Distance}{circumference}$$

Circumference: $$\pi d=70\pi=(70*\frac{22}{7})\approx{220}cm$$

Distance = $$100,000 cm$$

Number of revolutions:
$$\frac{Distance}{circumference}=\frac{100,000cm}{220cm}\approx{455}$$ revolutions

Answer B
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Re: A bicycle tire has a diameter of 70 centimeters. Approximately how man  [#permalink]

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12 Apr 2018, 10:25
Bunuel wrote:
A bicycle tire has a diameter of 70 centimeters. Approximately how many revolutions does the tire make if the bicycle travels 1 kilometer. (1 kilometer = 100 meters = 100000 centimeters)

A. 150
B. 450
C. 900
D. 1500
E. 2200

$$Number of revolutions =\frac{Distance}{circumference}$$

Circumference = $$\pi d=70\pi=(70*\frac{22}{7})\approx{220}cm$$

Distance = $$100,000 cm$$

Number of revolutions = $$\frac{Distance}{circumference}=\frac{100,000cm}{220cm}$$

Here we can make 220 to be 200 to ease the calculation. The answer choices helps to make the approximation.

Number of revolutions = $$\frac{Distance}{circumference}=\frac{100,000cm}{200cm}$$ = $$500$$

The number must be less than 500.

450 is the closest to 500

Answer B
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Re: A bicycle tire has a diameter of 70 centimeters. Approximately how man  [#permalink]

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16 Apr 2018, 15:14
Bunuel wrote:
A bicycle tire has a diameter of 70 centimeters. Approximately how many revolutions does the tire make if the bicycle travels 1 kilometer. (1 kilometer = 100 meters = 100000 centimeters)

A. 150
B. 450
C. 900
D. 1500
E. 2200

(note: although we are using the given conversion, 1 kilometer = 1,000 meters)

The circumference of the tire is 70π = 70 x 3.14 = 219.8 cm, which is about 220 cm. Thus, 1 revolution of the tire is about 220cm.

Since 1 km = 1,000 m and 1 m = 100 cm, so 1 km = 1,000 x 100 = 100,000 cm. Thus in 100,000 cm, the number of revolutions is 100,000/220 ≈ 454 ≈ 450 revolutions.

Answer: B
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Re: A bicycle tire has a diameter of 70 centimeters. Approximately how man &nbs [#permalink] 16 Apr 2018, 15:14
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# A bicycle tire has a diameter of 70 centimeters. Approximately how man

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