Answer:
240.3
Explanation:
Remember SohCahToa for the trig. ratios. You always divide two sides.
'o' is opposite side. 'a' is adjacent side. 'h' is hypotenuse side.
Using alternating angles you can find the angle I marked blue (see diagram below). Because the 31° is parallel to the bottom side of the triangle, you can use alternating angles (Z pattern), where both 'insides' of the Z have the same measure.
The blue angle will be our angle of reference (angle we are talking about) represented by this symbol θ.
Since we need to find 'y', the opposite side, and we know 400ft is the adjacent side, use the tangent ratio.
tanθ = opposite / adjacent
tan31° = y / 400ft Substitute what you know.
y = (400ft)tan31° Isolate 'y'. Multiply 400ft and tan31°.
y = 240.344......ft Exact answer on calculator
y ≈ 240.3ft Answer rounded to nearest tenth
The nearest tenth is the first decimal. Since the second decimal is '4 or less', you round down, keeping the digit of the first decimal the same.
If the second digit was '5 or more', then you would round up.