In a school, one bell rings after every 30 minutes while the other rings after every 35 minutes. If the two bell rang together at 8:15 a. m., at what. Time did they ring together next?

Answer 1

LCM(35,90) = 630
so what is 630 minutes after 8:15 ?

Answer 2

7 * 30 = 6 * 35 = 210

210 minutes after 8:15 a.m.

Answer 3

oops. R_scott was right. I guess I better clean my glasses.