HCF and LCM of two numbers are 7 and 140 respectively. If the numbers are between 20 and 45, the sum of the numbers is: 

The least multiple of 13, which on dividing by 4, 5, 6, 7 and 8 leaves remainder 2 in each case is 

Two pipes of length 36 metre and 40 metre are to be cut into equal pieces without leaving any extra length of pipe. Find the number of such pieces if pipes are to be cut of maximum length.

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

If the ratio of two numbers is 13 : 15 and their L.C.M. is 39780. Then the numbers are?

The H.C.F. of two numbers is 8. Which one of the following can never be their L.C.M? 

The traffic lights at three different road crossings change after 24 seconds, 36 seconds and 54 seconds respectively. If they all change simultaneously at 10 : 15 : 00 AM, then at what time will they again change simultaneously? 

Four runners started running simultaneously from a point on a circular track. They took 200 seconds, 300 seconds, 360 seconds and 450 seconds to complete one round. After how much time do they meet at the starting point for the first time?