Rebecca have 9/10 of a yard of ribbon then she gave 720s of a yard to a friend how much does she have left
To find out how much ribbon Rebecca has left after giving some to her friend, you need to subtract the amount she gave from the amount she initially had.
Rebecca initially had 9/10 of a yard of ribbon, and she gave away 720s of a yard. To make the units consistent, we need to convert 9/10 to the same denominator as 720s, which is 10.
To do that, we multiply the numerator and denominator of 9/10 by 7, since 10 multiplied by 7 is 70:
9/10 * 7/7 = 63/70
Now that both fractions have the same denominator, we can subtract them:
63/70 - 720/1000
To simplify this subtraction, we need to find a common denominator, which is the least common multiple of 70 and 1000. The least common multiple of these two numbers is 7000.
Converting both fractions:
63/70 * 100/100 = 6300/7000
720/1000 * 7/7 = 5040/7000
Finally, we subtract these fractions:
6300/7000 - 5040/7000 = (6300 - 5040)/7000 = 1260/7000
Now, we can simplify this fraction by dividing both the numerator and denominator by their greatest common divisor, which is 140:
(1260/140) / (7000/140) = 9/50
Therefore, Rebecca has 9/50 of a yard of ribbon left after giving away 720s of a yard to her friend.