Question

6. Kathleen needs 240 valid signatures on a petition to get a crosswalk installed on her street. She knows

Answer 1

Kathleen must get 300 signatures to make sure she will have enough valid signatures for the crosswalk

Solution:

Given that Kathleen needs 240 valid signatures on a petition to get a crosswalk installed on her street

She knows  that about 20% of the signatures will not be valid for a variety of reasons

Let "x" be the number of signatures

invalid signature = 20 % of x

valid signatures = 240

Then, according to question,

total number of signatures - invalid signatures = 240

x - 20 % of x = 240

$x - 20 \% \times x = 240\\\\x - \frac{20}{100} \times x = 240\\\\x - 0.2x = 240\\\\0.8x = 240\\\\x = 300$

Therefore, she must get 300 signatures so that she will have enough valid signatures for the crosswalk