Envelope/address coding puzzle: number of envelopes with correct address

A triangle PQR is such that 3 points lie on the side PQ, 4 points on QR and 5 points on RP respectively. Triangles are constructed using these points as vertices. What is the number of triangles so f…

What is the sum of all four digit numbers formed by using all digits 0, 1, 4, 5 without repetition of digits ?

Four digit numbers are formed by using the digits 1, 2, 3, 5 without repetition of digits. How many of them are divisible by 4?

In an examination, a question paper has 12 questions divided into Part I and Part II containing 5 and 7 questions. A student must attempt 8 questions, selecting at least 3 from each part. Number of w…

The number of ways in which the letters of the word “ALGEBRA” can be arranged so that two A's are not adjacent, are