Originally Posted by

**Soroban** Hello, HNCMATHS!

We don't need any fancy formulas, do we?

We have six equally-spaced numbers:. . $\displaystyle

81\; \underbrace{\qquad}_d\; ? \; \underbrace{\qquad}_d \; ? \; \underbrace{\qquad}_d \; ? \; \underbrace{\qquad}_d \;? \; \underbrace{\qquad}_d \; 954 $

The range is: .$\displaystyle 954-81 \:=\:873$

So the numbers are spaced: .$\displaystyle d\:=\:\tfrac{873}{5} \,=\,174.6$ apart.

The six speeds are: .$\displaystyle 81,\;255.6,\;439.2,\;604.8,\;779.4,\;954$