Find the value of $$ {1\over{2×5}}+{1\over {5×8}}+{1\over {8 × 11}}+......{1\over {23 × 26}}=?$$

Four bells ring at the intervals of 5, 6, 8 and 9 seconds. All the bells ring simultaneously at some time. They will again ring simultaneously after: 

A shopkeeper bought 15 kg of rice at the rate of Rs.29 per kg and 25 kg of rice at the rate of Rs.20 per kg. He sold the mixture of both types of rice at the rate of Rs. 27 per kg. his profit in this transaction is___

When the average age of husband, wife and their son was 42 years, the son got married and a child was born just one year after marriage. When the child turned to be 5 years, the average age of the family becomes 36 years. What was the age of daughter-in-law at the time of marriage?

What is the volume of a cube whose side is 7.5 cm?