Quantitative Aptitude - Arithmetic Ability Questions

Given total number of students in the class = 21

So each student will have 20 greeting cards to be send or receive (21 - 1(himself))

Therefore, the total number of greeting cards exchanged by the students = 20 x 21 = 420.

As these three strategies P, Q and R are independent so these will cut cost one after the other.
If initial cost is Rs 100, then
20% cost is cut after initializing strategy P, then cost will remain 80% = 80
further 30% cost is cut after strategy Q, then cost will remain 70% of 80 = 56
further 10% cost is cut after strategy R, then cost will remain 90% of 56 = 50.4

Thus final cost remains 50.4 % of the original cost. Hence net saving is 100 - 50.4 = 49.6 %.

Given Series is 5, 14, 42, 107, 233, _?

5, 14, 42, 107, 233, _?

Differences is 9, 28, 65, 126

9 = 2^3 + 1

28 = 3^3 + 1

65 = 4^3 + 1

126 = 5^3 + 1

Now, next difference must be 6^3 + 1 = 217

Hence, next number in the given series = 233 + 217 = 450.

Profit would be maximum if watches are brought for Rs. 200 and sold for Rs. 425
Profit = Rs. (425 - 200) = Rs. 225
Profit of 9 watches = Rs. 225 x 9 = Rs.2,025.

Multiples of 3 below 20 are 3, 6, 9, 12, 15, 18
Multiples of 5 below 20 are 5, 10, 15, 20
Required number of possibilities = 10
Total number of possibilities = 20
Required probability = 10/20 = 1/2.