What is the greatest common divisor of 28 and 98?

Answer 1

You have to find the divisors of each numbers. To do so try and divide it by prime numbers starting with 2 and increasing each time you cannot divide. Repeat until you have 1.

So, can you divide 28 by 2 ? Yes, and you have 14

Can you divide 14 by 2 ? Yes, and you have 7

can you divide 7 by 2 ? no. By 3 ? no By 5? no. BY 7 ? Yes and you have 1.

So, 28 = 2 * 2* 7

Now for 98:

98 = 2 * 49

49 = 7 * 7

7 = 7 * 1

So, 98 = 2*7*7

To find the greatest common divisor, you now need to look for the common part in each number breakdown into prime numbers:

In our example: 2*2*7 vs 2*7*7, you find that the common part is 2*7. So the GCD of 28 and 98 is 14.