Mathematics

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September 26th 2012, 03:51 AM
Spixol123

Mathematics

Hi i have an aptitude test and i get question like the one below and i just need help learning and understanding the easiest way to work it out.

A car travels from 9 a.m. to 11.10 a.m. at an average speed of 83 km/h. What distance is travelled, to the nearest km?

A) 176 km (B) 178 km (C) 179 km (D)180 km

I got the answer 174 km but as u see there is not an option lol.

Please could someone explain to me the most easiest way to work this out?
September 26th 2012, 05:47 AM
Soroban

Re: Mathematics

Hello, Spixol123!

I think I know what you did . . .

Quote:

A car travels from 9:00 a.m. to 11:10 a.m. at an average speed of 83 km/h.
What distance is travelled, to the nearest km?

. . A) 176 km . (B) 178 km . (C) 179 km . (D) 180 km

I got the answer 174 km, but as you see that is not an option. lol

From 9:00 to 11:10 is two hours and ten minutes.

That is: . $2 + \tfrac{10}{60} \:=\:2\tfrac{1}{6}$ hours.

$\text{Distance} \:=\:\text{Speed} \times \text{Time}$

. . . . $D \;=\;83 \times \tfrac{13}{6} \;=\;\frac{1079}{6} \;=\;179.8333...$

Got it?
September 26th 2012, 08:17 AM
Spixol123

Re: Mathematics

Perfect. Thanks. Is there any other way to work this question out. I tried adding 83 together and getting 166 but then needed to figure out what 10mins equals too?
September 26th 2012, 08:49 AM
ebaines

Re: Mathematics

Quote:

Originally Posted by Spixol123

Perfect. Thanks. Is there any other way to work this question out. I tried adding 83 together and getting 166 but then needed to figure out what 10mins equals too?

So you found that in two hours it goes 166 Km, and want to add the distance cobvered in an additional 10 minutes? Like Soroban said, distance = rate times time, but we need to be careful to keep everything in consistent units. If speed is given in kilometers per hour you must multiply by time in hours to get the distance. Alternatively you could convert the speed from KPH to kilometers per minute and then multiply by time in minutes. The math for each approach is like this:

Distance = rate times time, where time (in hours) = $10 \ min \times \frac {1 \ Hr}{60 \ Min} = \frac 1 6 \ Hr$
$D = 83 \frac {Km}{Hr} \times \frac 1 6 \ Hr = 13.833 Km$

Or:

Rate (in Km/min) = $83 \frac {Km}{Hr}\times \frac {1 \ Hr}{60 \ Min} = 1.3833 \frac {Km}{Min}$
$D = 1.3833 \frac {Km}{Min} \times 10 \ Min = 13.833 Km$ .

So you would add 13.833 Km covered in the last ten minutes to the 166Km for the first two hours to get a total distance of 179.833 Km. Hope this helps.
September 26th 2012, 09:00 AM
Spixol123

Re: Mathematics

Awesome!! thanks to both!