30/210 simplified to 1/7 i think
Remark
For every 3 units for NP will be 4 units. You can set up a proportion.
3*NP = 4*45
3*NP = 180 Divide by 3
NP = 180/3
NP = 60
Answer C
Remark
You are dealing with a right angle triangle. You can use one of Sin(x) Cos(x) or Tan(x). Since the Hypotenuse is involved and since you are given the adjacent side, Cos(71) is what you will need.
Solution
H = BC
Cos(x) = adjactent / hypotenuse
Cos(71) = 6.3 / H Multiply both sides by H
H * Cos(71) = 6.3 Divide by Cos(71)
H = 6.3 / cos(71) Cos(71) = 0.32557
H = 6.3 / 0.32557 Divide
H = BC = 19.351 Answer
That would be 30 minutes since 2 1/2 hours equals 150 minutes, a fifth of 150 is 30.
