Multiples and common multiples
A multiple of m is m × k for a whole number k. The multiples of 7 are 7, 14, 21, 28, 35, and so on, which is the 7 times table. The 20th multiple is 7 × 20 = 140.
Common multiples of several numbers are exactly the multiples of their least common multiple. For 4, 6 and 10: LCM(4, 6) = 12, and LCM(12, 10) = 120 ÷ 2 = 60. So the common multiples are 60, 120, 180, …
Checking a multiple
x is a multiple of m when x ÷ m leaves remainder 0. 91 ÷ 7 = 13 remainder 0, so 91 is a multiple of 7, even though it doesn't look like one. 0 is a multiple of every number.