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# Math

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2 snowplows can clear a road 12km x 4 m in 3 hours. How long will take for 10 snowplows to clear a road 2km x 12m.

My solution is 18 minutes but in book answer is 9 minutes. Am I wrong or there is error in book?

Jan 24, 2021

#1
+1

You are right answer is 18 I also got 18

In first case area is 12000*4=48000m

2 person clear road at 3 hour so one person can do at 2*3 = 6 hour

Than 10 person can do this same work at 6/10= .6hour =36 minutes

In second case area is 2000*12=24000

So by logic time to do this work is 18 min

Jan 24, 2021
#2
+11086
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2 snowplows can clear a road 12km x 4 m in 3 hours. How long will take for 10 snowplows to clear a road 2km x 12m.

Hello Guest!

$$N=W/t$$

$$N_{sp}=\dfrac{12km\cdot 4m}{2\cdot3h}\cdot \dfrac{1000m}{km}=8000m^2/h$$

$$t=\dfrac{W}{N_{sp}}$$

$$t=\dfrac{2km\cdot 12m}{10\cdot 8000m^2/h}\cdot \dfrac{1000m}{km}$$

$$t=0.3h\cdot\dfrac{60min}{h}=\color{blue}\ 18min$$

10 snowplows clear a road of 2km x 12m in 18min.

You're right.

!

Jan 24, 2021
edited by asinus  Jan 24, 2021
#3
+12485
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2 snowplows can clear a road 12km x 4 m in 3 hours. How long will take for 10 snowplows to clear a road 2km x 12m.

My solution is 18 minutes but in book answer is 9 minutes. Am I wrong or there is error in book?

Jan 24, 2021
#4
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3 hr 2s / (12*4 km2 )     *   2*12 km2/ 10s =  .3 hr        or       18 minutes

Jan 24, 2021
#5
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Yep. I get .3 hours that’s 18 minutes.

Jan 24, 2021
#6
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I get 18 mins too

Jan 24, 2021
#7
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60/.3 = 18 so its 18 minutes

Jan 24, 2021
#9
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Close!   Haha    60 / .3 = 200

60 X .3  = 18

Guest Jan 24, 2021
#8
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Wait I get 9 minutes Why am I getting 9 minutes when everyone else is getting 18 minutes

I must have made a mistake

Jan 24, 2021
#10
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You made a mistake its 18 minutes I just rechecked my work. Its .3 hours that is 18 minutes.

Jan 24, 2021
#11
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Oh I did make a mistake. Its a good thing everyone is checking its easy to get wrong!!!

Jan 24, 2021
#12
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what are the amount and compound interest for $720 for 3 years at 5% per annum Jan 24, 2021 #13 0 what are the amount and compound interest for$720 for 3 years at 5% per annum

Wierd place to post this......

for 5% annully compounded interest ;

final amount = 720(1.05)3

amount of Interest = 720  (1.05)-750

Guest Jan 24, 2021