Question

Of the 400 candidates who were interviewed for a position at a call center, 200 had a laptop, 140 had a calculator and 280 had a mobile phone. 80 of them had both, a laptop and a calculator, 60 had both, a calculator and a mobile phone and 120 had both, a laptop and mobile phone and 20 had all three. On the basis of above information answer the following questions.
Question 1. How many candidates who attended the interview had at least one of the three gadgets?
How many candidates had none of the three?
How many candidates have only laptops?

Answer 1

180 students have one or more device.120+90+70=280 which shows that 100 students have more than one device. Looking at the overlaps: x number of students have all three devices. So 50-x+40-x+30=100. So x=10. The overlaps can then be calculated:Calculator + mobile, no laptop, 20. Laptop + mobile, no calculator, 40. No laptop, 50+20 (who don't have any of the devices)=70.