Qs (1 Viewer)

[pc4pc]

1. Find the radius and height, correct to 2 decimal places, of a cylinder that holds 200cm^3, if its surface area is to be a minimum.

2. The cost of running a car at an average speed of v km/h is given by
c = 150 + v(to the power of two)/80 cents per hour.
Find the average speed, to the nearest km/h, at which the cost of a 500km trip is a minimum.

thankyou:wave:


answers are
1. r=3.17, h=6.34
2. 110km/h

 

[cl3nta]

that first one is interesting. I was trying to use simultaneous equations but yea couldn't because r and h are variables. Nevertheless, I'll leave you to play around cos I have to go fiddle with integration

V=200cm^3
V=pir^2h (formula for cylinder)
so,
200=pir^2h
h=200/r^2pi (1)

SA=2pir^2 + 2pirh

Have fun and good luck

 

[pc4pc]

that first one is interesting. I was trying to use simultaneous equations but yea couldn't because r and h are variables. Nevertheless, I'll leave you to play around cos I have to go fiddle with integration

V=200cm^3
V=pir^2h (formula for cylinder)
so,
200=pir^2h
h=200/r^2pi (1)

SA=2pir^2 + 2pirh

Have fun and good luck

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