The table below shows the grades of 120 students who joined a Mathematics competition. Grade A is the best grade and Grade E is the worst grade.

Grade	A	B	C	D	E
Number of students	15	27	54	18	6

Only $\frac{7}{20}$ of the students made it through to the second round.
What was the minimum grade required to go through to the second round?

1. Calculate the number of students who made it to the second round.

$\frac{7}{20} \times 120 = 7 \times 6 = 42$

2. Determine the minimum grade by accumulating students from the best grade.

Number of students with Grade A = $15$
Number of students with Grade B = $27$
Total students with Grade A or B = $15 + 27 = 42$
Since exactly 42 students made it through, the cutoff is Grade B.