If pq+qr+rp=0 then find the value of $$ {p^{2}\over {p^{2}-qr}}+{q^{2}\over {q^{2}-rp}}+{r^{2}\over {r^{2}-pq}}$$

What will come in place of question mark(?) in the following number series?
10, 14, 25, 55, 140 (?)

A man loses 20% of his money. After spending 25% of the remainder, he has Rs.480 left with him. How much money did he originally have?

In the following figure if OA=10 and AC=16, then OB must be:

Find measure of central angle of the arc whose length is 22 cm and radius of the circle is 28 cm?

At what time between 6 to7 O ' clock minute and hour hand will coincide? 

The price of 6 pencils is Rs. 30 and that of 12 pens is Rs. 120. What is the average price of 50 pencils and 50 pens?