Answer:
7 feet
Step-by-step explanation:
Length of one piece of string = 28 feet.
Length of the second string = 42 feet.
Since the number of required pieces was not given but many are required, the greatest length can be determined by;
If the maximum length is 7 feet, then:
the number of pieces from 28 feet long string =
= 4
Also,
the number of pieces from the 42 feet lone string =
= 6
Total number of 7 feet strings that she can make = 4 + 6
= 10
Since many pieces are required, the greatest length she can make is 7 feet. If she increase the length to 14 feet, the number of pieces would be 5 which limit the required number.