Pfn Interview Questions, Process, and Tips

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When none of the digits are repeated:

The hundred’s place can be filled by any of the digits: 2, 3, 5, 6, 7 or 8 except the one which has already been used at the thousand’s place, so it can be filled in 5 ways.

Similarly tens’ place can be filled in 4 ways: only those 4 numbers which have not been use either at hundred’s or thousand’s place.
Unit’s place can be filled in only 3 ways. So, total number of nos. Possible =4×5×4×3= 240

3 minutes

121

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Initially, potatoes have 99% water by weight ; which means they have 1% solid non-water content.

1% of 100 kg = 1 kg

Now even when they dehydrate,this 1kg solid mass remains constant.

It is given that finally, 98% is water by weight , which implies that 2% is non-water solid.

This means 2% of total weight = 1 kg

Total weight *2/100 = 1 kg

Therefore, total weight finally = 50 kg.

answer :36

2nd

Initially (2*33 + 1*24)/(2+1) = 30p a gm
So, cost for 100g = 100*30 = 3000p

Later, (1*33 + 2*24)/(1+2) = 71/3 p a gm.
So, cost for 100g = 100*(71/3) = 2366.67p

He saves 3000 – 2366.67 = 633.33p

Concept of weighted average.

pass English =80%
fail=100-80=20%
pass Math = 70%
fail in Math=100-70=30%
fail in both=10%
total fail students= fail in Eng+fail in Math-common
= 20+30-10=40%
if 40% fail then 60% will pass
let total students=x
hence
60% 0f (total students)=144
60/100 of (x)= 144
x=(144×100)/60
X=240
total students=240