## 4-digit number

How many 4-digit numbers are there with no digit repeated?
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## Triangular matrix

If U1, U2 are upper triangular and L1, L2 are lower triangular, which of the following are triangular?  U1 + U2  U1U2  U12  U1 + L1  U1L1  L1 +...
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## Probability of Positive Integers being Coprime !

What is the probability that six randomly chosen positive integers are relatively prime ?

## The sunrise problem

Two women start walking at the sunrise, one from point A to B and another from point B to A. The pass each other exactly at noon. The first...
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## Calculate A+B+C+D

Find (A + B + C + D) such that AB x CB = DDD, where AB and CB are 2-digit numbers and DDD is a 3-digit number.
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## Number of Combinations !

In how many ways can you select 7 letters from the word MISSISSIPPIRIVER regardless of their orders?

## Puzzle

Can you solve in 1 minute?? Can you solve in 50 seconds? can you solve in 30 seconds? can you solve in 10 seconds? Mention the time that you...
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## Simplify

Simplify: 4(x-3)-x(a-2)-3
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## Find highest share?

If 500 is shared in the ratio 2：3：5, what will be the highest share?

## Speed of the boat in stream

Upstream boat speed=18km/hr and this speed is 500% more than stream speed. What is the downstream speed of the boat? Source
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## Faster runner, slower runner

Two runners start on a straight one-mile race track. The slower runner S is given a handicap and starts first. The faster runner F then starts and after 4...
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## Distance Between Two Places & Time Taken !

Manish and Rajni start from a place M at the same time to reach another place R. Manish travels at a constant speed of 21 kmph, while Rajni starts with...
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## How Many Numbers Divisible ?!

How many integers from 100 to 10000, inclusive, are exactly divisible by 6 or 11 or 14 or 15 but neither divisible by 30 nor by 42 ?