11 observations are arranged in ascending order. If 10 and 9 are respectively the arithmetic means of observation on even and odd places, then the mean of all 11 observations is –

A, B and C can do a work in 20, 30 and 60 days respectively. In how many days can A complete the work, if he is assisted by B and C on every third day?

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…

How many 4-letter words with or without meaning, can be formed out of the letters of the word, 'LOGARITHMS', if repetition of letters is not allowed?

In how many different ways can four books A, B, C and D be arranged one above another in a vertical order such that the books A and B are never in continuous position?

How many three-digit numbers can be generated from 1, 2, 3, 4, 5, 6, 7, 8, 9 such that the digits are in ascending order?