Answer:
<em>sorry i don't know the answer:(</em>
Answer:
GCF= 1
LCM= 1680
Step-by-step explanation:
GCF= Find the prime factorization of 21, 21 = 3 x 7
Find the prime factorization of 80, 80 = 2 x 2 x 2 x 2 x 5
Then multiply the prime factors both numbers have in common
LCM= multiply the two numbers together and ignore all negative signs
There are many possibilities. An example is 
.
Get them to have a common denominator. 100 is the common denominator, so change 7/10 and 3/5 to have a denominator of 100. 7/10=70/100 and 3/5=60/100. So from least to greatest it will go 8/100, 3/5, 7/10.
Well if each band needs 15.5 inches and she needs to make 12 headbands she needs 15.5 inches 12 times. Now you can add 15.5 + 15.5 +15.5 (so on) 12 times or you can do it the easier way and do 15.5 times 12. this comes out to 186 inches of ribbon. She estimated 160 inches of ribbon, this is unreasonable because it is significantly less that 186.
