What effect does doubling the length and width have on the perimeter

Determine the number of girls in a math class with 87 boys if there are 25 girls for every 75 boys

On a string instrument, the length of a string varies inversely as the frequency of its vibrations. an 11-inch string has a frequency of 400 cylces per second. find the frequency of a 10-icnch string.

Type the correct answer in each box. spell all the words correctly, and use numerals instead of words for numbers. if necessary, use / for the fraction bar(s).