Story Problem

Question

The first stage of a rocket buns 28 seconds longer than the second stage.  If the total burning time for both stages is 152 seconds, How long does each stage burn?

Answer 1

Sometimes using any sort of variables trips up students that aren't so used to assigning them at all, especially multiple letters, subscripts, etc.  I try writing things out in words that look "mathy" or drawing a picture first and combining groups if that helps, especially if you aren't great at writing equations regularly, but usually know "how to do it."

 

So this one could also look like what Arturo wrote just a little more basic:

First stage time + (First stage time - 28 seconds) = 152 seconds

x + (x - 28) = 152

         2x-28 = 152

etc. and so forth.  Just don't forget they asked for BOTH times not just one of them, which is what finding only x will do! 

 

Either way will get you there and that's the beauty of math.  Hope that helps.

Answer 2

T₁ = time the first stage burns

 

T₂ = time the second stage burns

 

Given:

 

T₁ = T₂ + 28

T₁ + T₂ = 152

 

Then

 

(T₂ + 28) + T₂ = 152 ⇒ T₂ = (152 - 28) / 2 = 62 seconds

 

T₁ = T₂ + 28 = 62 + 28 = 90 seconds