In examination 30% students failed in Economics and 20% failed in History. If 10% failed in both and those who passed in both numbered 600, then what is the total number of students who appeared in the examination?

Option 2 : 1000

Number of student who passed in both subject = 100% - (20 + 10 + 10) = 60%

60% X =600

X= 1000

Hence, 1000 is the total number of students appeared in the examination.

{Short trick: we can draw the venn diagram for the above case as follows:

[ alt="F1 Resham.R 29-12-20 Savita D9" src="//storage.googleapis.com/tb-img/production/20/12/F1_Resham.R_29-12-20_Savita_D9.png" style="width: 190px; height: 131px;">

From the diagram we get that total failed students in % is = 20% + 10% + 10% = 40%

 That means 60% of the students are passed in the examination.

Given in the question that 60% = 600

So, 100% = (600/60) × 100 = 1000