Aptitude - Time and Work - Discussion

25% efficient means Tanya takes 15 days.
Both 1 day work=1/20+1/15=7/60.
Tanya work=7/60-1/20=1/15.
Why can't the answer be 15?

As Sakshi can do 1/20 per day, Tanya can do 25% more per day than Sakshi.
So, [(1/20)+(1/20)*(25/100)].

i.e. 5/80 i.e 1/16 i.e 16 days.

Taniya can do 25% more than Sakshi
i.e., Taniya = 100%+25% = 125%of Sakshi
Sakshi 1 day of work is 1/20 then 125% of 1/20
i.e., 1.25*(1/20) = 1/16 in one day for Taniya
So, the work will be completed in 16 days.

Anyone explain the correct answer.

Solve by the Trick:

100 * M/100 + X.
Here, M = day.
X= efficiency.
Therefore:

100 * 20/100 + 25,
2000/125,
16 days.

Sakshi can do a piece of work in 20 days and Tanya is 25% more efficient than Sakshi that means

125% of Work by Sakshi in ------------> 20 days.
100% of Work by Tanya ---------------> x.


By Cross Multiplication we get;

125% * x = 100% * 20,
=> (125/100) * x = (100/100) * 20,
=> x = (100/125) * (100/100) * 20,

After Cancellation You'll get Result as 16 days.

@All.

Here Tanya is 25% more efficient than Sakshi. So why can't we take Tanya as 100 and Sakshi as 75. It can be understood from the basic concept of percentages that if A is 25% more than B, B is how much percent less than A and that will never be 25.

Let B=100 => A=125. Difference= 25. How much is B less than A = (25/125)*100 = 20%. The change is to be taken from A i.e 125 and not 100.

Similarly, if Tanya is 25% more efficient than Sakshi, then Sakshi is 20% less efficient than Tanya and not 25%.

So going by this, if you take 80 instead of 75, you will get the same answer which is also the only correct answer.

Tanaya is - 25% more efficient than of (Sakshi).

So let's assume,

Sakshi takes 20 days to travel 2000km with a speed of 100km/ day
So Tania should take, X days to travel 2000km with the speed of 125% of (100km/day)

So speed should be, 100/100 * 25.
So time would be, 2000/125 = 16 days.

Yes, you are correct @Okley.

Why can't 15 be the answer?
25%of 20=5 subtracts from 20 then gets 15, right?

Let us solve it easily:

So, Tanya is 25% more efficient than Shaksi which means Tanya is 100% then Sakshi will be 125%
Now: Sakshi:125--> 20 days
Tanya :100-->x.
By cross multiply(x)-->x=20*100/125.
= 16days.