Plz tell me how to do question 18

750kmph

Step-by-step explanation:

Average is sum of all parts divided by the number of parts.

Let Stot be average speed for total trip (800kmph).

Let S1 be speed for first quarter of trip (950kmph).

Let S2, S3, and S4 be the speeds of each of the remaining quarters respectively.

Let Sans be the average speed for the remaining three quarters of the trip (a.k.a. The Answer!).

Stot = (S1 + S2 + S3 + S4) / 4

800kmph = (950kmph + S2 + S3 + S4) / 4

3200kmph = 950kmph + S2 + S3 + S4

3200kmph - 950kmph = 2250kmph = S2 + S3 + S4

Divide both sides by 3.

2250kmph / 3 = (S2 + S3 + S4) / 3 = Sans

Sans = 750kmph

12.4, 12.387, 12.26, 12.252, 6.241, 6.2, 6.015, 6.009, 1.411, 1.2, 1.056, 1.007, 0.31,   0.13, 0.5, 0.04

step-by-step explanation:

ur welcome : )