[Aptitude] 3-in-1 Trick: Percentage change, Time n Speed, Inflation consumption, Product consistency method
Following three types of questions routinely appear in aptitude exams and all three can be solved with same "STD" formula approach.
Speed x Time = distance.
Let's concentrate on third question right now.
If a car increases the speed by 25%, then in how much % less time will you reach the destination?
Step 1: Put any valuesSpeed = 100 kmph
Time =100 hours.
Speed x time = distance.
=100 x 100 =10,000
Step 2: Increase / Decrease one thingNow we increase the speed by 25% (given in the problem)
Speed =100+25= 125 kmph
Time= we've to find out.
Distance = same 10,000 km. (we found in Step 1)
Again use STD fomula
Speed x time = distance
125 x time = 10,000
Time = 10,000/125=80 hours.
Compare: old time was 100
New time is 80.
How much decrease?
Answer: if you increase speed by 25% then time will decrease by 20%.
In the first two problems (petrol price and Jethalal), you apply the same STD fomula and you'll get the same answer.
6 x 4 =24
Now if you increase the 6 to 8
8 x ? =24
Obviously 4 has to decrease any become 3, because
8 x 3=24.
Because the final product has to remain consistent, if you increase one thing (price of petrol, speed of a car) then second thing (volume of petrol, journey time) must decrease to keep the product consistent.
If Jethalal's age is 25% more than Tarak Mehta. Then by how much percentage, Tarak Mehta's age is less than Jethala?The principle is same. Rephrase the question: if speed increased by 25%, then time will decrease by what %? Do as directed in first problem and you'll get the same answer = 20% less.
If price of petrol increases by 25%, then by how much percent must a person decrease his consumption so that expenditure remains the same?We know that
Unit Price x quantity = total Expenditure.
e.g. if price of one ball pen is 10 rupees and you buy 10 units of pen,
the total Expenditure = 10 x 10 =100.
But to keep things simple, just remember single "STD" formula.
Speed x time =distance.
Now rephrase the question as ": if speed increased by 25%, then time will decrease by what %?
Plug in the values; you'll get the same answer from first problem. 20% decrease.
If Salman khan is 50% less tall than Big B. And by what percentage Big B is taller than Salman Khan?
Rephrase: if you decreased the speed of your car by 50%, how much % more time will it take to reach destination?Read more »
Monday, April 2, 2012
Aptitude and Science Topics from Mrunal
Source : Mrunal's blog