Before adding dissimilar fractions (fractions with different denominator), you have to make the fractions similar first. To make the fractions similar, find the Least Common Multiple of the denominator. In this case, the LCM is 10. Then rewrite the fractions using the LCM as the denominator.
9/10 = 9/10; 4/5 = 8/10
You can now proceed with addition -
9/10 + 8/10 = 17/10 or 1 7/10
The total length of the ribbon used is expressed as r and is a product of the number of gifts (g) and the length of ribbon tied in each gift. This relationship may be expressed by the equation,
r = (25) x (g)
Answer: Multiplying and Dividing Decimals by Powers of 10
When you divide a decimal by a power of 10, simply move the decimal place to the left as many places as there are 0s in the power of 10.