Aptitude 3

Given are three practice quantitative aptitude questions with answers. These questions are generally easy to answer, but require good concentration as at times questions like these can get tricky.
Question 1
A shop sells floor tiles at Rs 48 per square meter. A building contractor employs a machine that polishes the tiles that damages 10% of the total number of tiles which cannot be used any more. Calculate the amount that needs to be paid by contractor to tile shop owner, if the hall is of a square shape and has a perimeter of 400 meters?
a) Rs 4,00,000 b) Rs 5,00,000 c) Rs 5,28,000 d) Rs 3,65,000
Answer : c) Rs 528000
Reason :
Cost of tiling the floor is at Rs.48 per square meter
Square shape hall perimeter = 400 meters
So side of square hall = 400 / 4 = 100 meters
Area of the hall = 100 x 100 = 10000 sq. meters
Assume that the tiles are sold as square meter blocks. Then, the area of the hall corresponds to 10000 number of tiles.
The contractor has to buy 10% more number of tiles than 10000 tile blocks to balance out the damage caused by polishing machine.
That is, he should buy 10000 X (110/100) = 11000 tile blocks.
Cost of each tile block is Rs.48
Total Cost for which tiles need to be bought = 48 x 11000 = Rs.528000
Question 2
A telecom communication college claims an average test pass rate of 76.8%. What is the least number of students required to achieve this result?
a) 249 b) 125 c) 62 d) 373
Answer : b) 125
Reason :
For such questions, it is advisable to go by options rather than trying to solve directly.
Essentially the questions is, if theoretically 76.8 students out of 100 pass (theoretical because, practically the number of students cannot be fraction like 76.8), what could be a minimum total number of students required so that the number of passing students is not a fraction but a whole number.
Starting by the smallest of the options, if we assume 62 is the total number of students, the number of students who pass = (76.8/100) X 62 = 47.6. This cannot be real as 47.6 is a fraction.
If we assume 125 as the total number of students, the number of students who pass = (76.8/100) X 125 = 96, which is perfectly possible as 96 is a whole number. Hence 125 is the answer.
For achieving 76.8% being a full number minimum number that is required is 125. 96 passes out of 125 gives an average of 76.8%
Question 3
There are 134 toys coloured red and white in a box. Two red toys are removed from the lot and now there are twice as many red ones as white ones. How many of red colour toys are there now?
a) 76 b) 86 c) 90 d) 88
Answer : d) 88
Reason:
Let R,W be the originally present number of Red and White toys respectively. Originally there were 134 toys. Hence,
R + W = 134 -->eq 1
After two red toys were removed, the number of red toys becomes twice that of the white toys.
R-2 = 2 W -->eq 2
Solving eq 1 and eq 2 we get
2 W = 134-W-2
3W = 132.
W= 44
R+44 = 134
R = 134 – 44 = 90
Originally there were R number of toys. But currently there only R - 2. Hence current number of red toys = 90 - 2 = 88