Question

The price of petrol goes up by 10%.By how much percent must a motorist reduce the consumption of petrol so that the expenditure on it remains unchanged?

Answer 1

lets assume initial 1 liter petrol cost=100
10% increase=100+10/100*100=110(that is 1 liter petrol cost is increased)
expenditure is same.that means we should buy the petrol only for 100 rupees.
increased amount of petrol is rs.10. that means this rs.10 is the part of amount in rs.110
now,
we should find what is the percentage of rs.10 in rs.110(because if you remove this rs,10,then you will get the same expenditure)
=10/110*100=9.09%
so 9% of consumption should be reduced.
3 years agoHelpfull: Yes(9) No(0)9% consumption has to be reduced.

because (91/100)*110 = 100
i.e 91 percent of (100 + 10) percent = 100 percent.7 years agoHelpfull: Yes(3) No(19)100/11 =9.09
3 years agoHelpfull: Yes(2) No(0)these questions are simple
u can use this trick
10% means 1/10 so reduce consumption by 1/10+1=1/11=9.09%3 years agoHelpfull: Yes(1) No(0)Let the initial price of petrol be: Rs. x
Let the initial consumption of petrol be : y
price after 10% increase:x+(10x/100)=1.1x
let z amount needs to be reduced.
by questn:
x*y=1.1*z*x*y
=>z=1/1.1
=>z=.9
so,
reduced amount=1-.9=.1
hence,
percentage reduction=10%
6 years agoHelpfull: Yes(0) No(21)9+1/11
the reduce factor is=10/11/*1002 years agoHelpfull: Yes(0) No(2)by using the formula r/100+r%*100
r=10 
10/100+10*100
10/110*100
100/110
10/11
9%1 year agoHelpfull: Yes(0) No(0)E=P*C
where E=expenditure
P=price
c=consumption

when E=0(does not change means)
E=p*c
0=10-x-10X/100
x=9.09%1 year agoHelpfull: Yes(0) No(0)(10/110)*100=9.09%7 Months agoHel

Answer 2

HEY DEAR ... ✌️

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Let the initial price of petrol be Rs. x

Then, price after increase of 10 % = 100 + (100*10)/100

= 100 + 10 

Price after increase of 10 % = Rs. 110

Now,

Reduction in consumption of petrol in percent = [{(110 - 100)}*100]/110

⇒ (10*100)/110

⇒ 100/11

⇒ 9.09 %

So, the motorists have to reduce the consumption of petrol by 9.09 %, so that the expenditure on it remains unchanged.

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HOPE, IT HELPS ... ✌️