Question 873773
A car travels d1 kilometers at s1 kilometers per hour.
 Then, it travels d2 kilometers at s2 kilometers per hour.
 Finally, it travels d3 kilometers at s3 kilometers per hour.
 Write a formula for the average rate of speed, s, over the entire trip.
:
Write a time equation
{{{(d1)/(s1)}}} + {{{(d2)/(s2)}}} + {{{(d3)/(s3)}}} = {{{(d1+d2+d3)/s}}}
:
s({{{(d1)/(s1)}}} + {{{(d2)/(s2)}}} + {{{(d3)/(s3)}}}) =  d1+d2+d3
:
s = {{{(d1+d2+d3)/((d1)/(s1)+(d2)/(s2)+(d3)/(s3))}}}