To find out how many inches elephant grass will grow in 7 days, we can multiply the growth rate per day (3 1/5 inches) by the number of days (7).
First, let's convert the mixed number 3 1/5 to an improper fraction:
3 1/5 = (3 * 5 + 1) / 5 = 16/5
Now, we can multiply the growth rate by the number of days:
(16/5) inches/day * 7 days = (16/5) * 7 = 112/5
To simplify the fraction, we can divide the numerator by the denominator:
112 ÷ 5 = 22 remainder 2
Therefore, the elephant grass will grow 22 2/5 inches in 7 days.