Here you have two number:
- a=3 - every third day Ivan goes to the gym to exercise;
- b=5 - every fifth day Gavin goes to the gym to exersise.
In order to find the first day Ivan and Gavin will be at the gym on the same day, you should count the least common multiple LCM(a,b.
Since numbers a and b are prime (3=1·3 and 5=1·5), then
LCM(3,5)=3·5=15.
Answer: the first day when Ivan and Gavin Will be at the gym on the same day is 15th day
