Question

What is the sum of 3/10 and 17/100

Answer 1

Sum is just another word for addition, so we have to add the two fractions.

3/10 + 17/100 

Find the LCD of the denominators, hence the name 'least common denominator'.  To do that, list out the multiples of each denominator and find the least common one.

Multiples of 10: 10, 20, 30, 40, 50, 60, 70, 80, 90, 100
Multiples of 100: 100

The least common denominator is 100. 
Now, divide the denominator of 3/10 to get the new denominator of 100. Whatever you do to the bottom, you have to do to the top.

(3 × 10) / (10 × 10) + 17/100

30/100 + 17/100

Since the denominators are the same now, we can add both of the numerators together.

(30 + 17) / 100

47/100

The answer is: 47/100 or 0.47.

Answer 2

3/10 + 17/100

first make the 10 of the 3/10 turn into a 100 so it will make the 100 of the 17/100.
to make 10 turn into a 100 you multiply it by 10. if you're going to multiply the bottom number by 10 then you have to do the same thing with the top number:
3/10 * 10/10
3*10=30
10*10=100

new equation:
30/100 + 17/100

now just add the top numbers and leave the 100's alone:
30/100 + 17/100
30+17=47
30/100 + 17/100 = 47/100