The sum of any three odd natural numbers is odd. Justify this statement with an example.

The traffic lights at three different road junctions change after every 40 seconds, 60 seconds and 72 seconds respectively. If they changed simultaneously together at 8 a.m at the junctions, at what time will they simultaneously change together again?

The sum of three prime numbers is 80. The difference of two of them is 4. Find the numbers.

Malarvizhi, Karthiga and Anjali are friends and natives of the same village. They work at different places. Malarvizhi comes to her home once in 5 days. Similarly, Karthiga and Anjali come to their homes once in 6 days and 10 days respectively. Assuming that they met each other on the 1^st of October, when will all the three meet again?

Explain your answer with reason for the following statements
A number is divisible by 9, if it is divisible by 3.