Question

Mr.Smith waters one of his plants every 10 days and another plant every 14 days. If he waters both plants today, when is the next time both plants will be watered?

Answer 1

After 140 days

Explanation:

The next time both plants will be watered together is simply the LCM of 10 and 14.

10 has multiples: 10, 20, 30, 40 , 50 ....

14 has multiples: 14, 28, 42, 56 ....

When will they next be equal?? That's the LCM.

We first do prime factorization of the numbers and then multiply each factor the greatest number of times it occurs in either number.

Prime Factorization

10 = 2 * 5

14 = 2 * 7

So,

LCM = 2^2 * 5 * 7 = 140

After 140 days