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Students are often troubled with combinatorics questions. TMost of them have never been given a proper explanation for the formulas for combination, variation, and permutation.

In the giv...

In order to simplify the problem, I will solve it without using fractions.

First,  we should find the least common multiple(LCM) of the days needed for Jack and Richard to paint a house. ...

This is an A* level GCSE Maths question. 'Solve' means we need to find what value x represents, but in the question this x appears on the denominator (bottom half) of the fractions which we can't use. ...

First of all, "second derivative", d²y/dx², is what you get when you differentiate the first derivative (dy/dx).

The second derivative can be used as an ea...

To work out averages we add up all of the ages and divide by the number of people in the group.

So that means in the first group, before the new person joined in, all the ages added up an...