99 points for brainliest

144

Step-by-step explanation:

4 triangles = 1/2 x 6 x 9 x 4 = 108

1 sq base = 6 x 6 = 36

total surface area = 36 + 108 = 144

if 3 triangles the base wouldn't be a square thus not possible to solve

144

Step-by-step explanation:

SA = Area of base + 4 area of triangles

6² + 4(9 × 6 × 1/2)

36 + 4(27)

= 144

4

step-by-step explanation:

7.9m and 4.3°

step-by-step explanation:

let east be +x and north be +y, x = distance * cos θ, y = distance * sin θ  

for 3.5 south, y = -3.5  

for 8.2, x = 8.2 * cos 30 and y = 8.2 * sin 30  

for 15 west, x = -15  

total x = 8.2 * cos 30 – 15 ≈ -7.9  

total y = -3.5 + 8.2 * sin 30 = 0.6  

magnitude = [(8.2 * cos 30 – 15)^2 + 0.6^2)]^0.5  

the magnitude is approximately 7.9 m  

tan θ = y/x = 0.6/-7.9  

the angle is approximately 4.3˚ north of west