The average of 30 results is 20 and the average of  other 20 results is 30. What is the average of all the results?

1) 24

2)48

3)25

4)50

Ranjit lent to Sujit Rs. 600 far 2 years and Rs. 150 to Alak far 4 years and received fram bath Rs. 90 as total interest.Interest being simple, the rate ,of interest charged per annum was  -

(1) 12%

(2) 6%

(3) 5%

(4) 2%

If A and B are square matrices of the same order such that AB = A and
BA =B, then (A +B ) is equal to:

1. A - B
2. A + B
3. AB
4. None of these