Practise Tests
1
The integers 1, 2, 3, 4, 5, 6 ………….. 40 are written on a blackboard. The following operation is then repeated 39 times: In each repetition, any two numbers, say a and b currently on the blackboard are erased and a new number a + b – 1 is written. What will be the number left on the blackboard at the end?
2
An intelligence agency decides on a code of 2 digits selected from 0, 1, 2, …, 9. But on the slip on which the code is hand written allows confusion between top and bottom, because there are indistinguishable. Thus, for example, the code 91 could be confused with 16. How many codes are there such that there is no possibility of any confusion?
Answer : Option A
Explanation:
Total digits that can be formed = 10C1 x 10C1 = 100.
The digits that still remain digits when turned upside down are 0, 1, 6, 8 and 9.
So codes that can create confusion are:
(69 would still be 69 when inverted)
(96 would still be 96 when inverted)
There are 20 such numbers.
Required numbers = 100 – 20 = 80
3
Let , ( n=0, 1, 2, …………), if = 0 then U(10) would be nearest to?
4
A change-making machine contains one-rupee, two-rupee and five rupee coins. The total number of coins is 300 and amount is Rs.960. If the number of one-rupee coins and two-rupee coins are interchanged, the value comes down by Rs.40. The total number of five rupee coins in the bag is
5
How many three-digit perfect squares are there, such that the hundreds digit, half the tens digit and the units digit are in geometric progression?
6
There is a seven digit number X in which the units digit and the first digit is divisible by 4. The middle digit is divisible by 3. A number Y is formed by reversing the digits of the number X [ex: If X = 1234567 then Y = 7654321]. What will be the remainder when X – Y is divided by 18?
7
There are two water tanks A and B, A is much smaller than B. While water fills at the rate of one litre every hour in A, it gets filled up like 10, 20, 40, 80, 160 in tank B. (At the end of first hour, B has 10 liters, second hour it has 20, third hour it has 40 and so on). If tank B is 1/32 filled after 21 hours, what is the total duration required to fill it completely?
8
A man ate 100 apple in five days daily he ate more than 6 apples when compare to previous day how many apples he ate in first day?
9
Three bells chime at intervals of 18 min, 24 min and 32 min respectively. At a certain time, they begin to together, what length of time will elapse before they chime together again?
10
The bacteria in a dish doubles every day. If we start with one bacteria on the first day the dish gets completely filled in 30 days.
If we start with one bacteria, in how many days the dish will be half filled?
