Can you please let me know how to solve this problem using equations.

I already solved it but mostly by trial and error.

I have $600 to spend.
I take 10 shopping trips.
Each trip I spend $10 more than the last trip.

How much did I spend on the first trip?

Thank you,

Alexander
Grade 6

 


Hi Alexander.

There is a way to solve this using introductory algebra.

If you spend $5 on the first trip, then the second trip costs $5 + $10 (which is $15).
If you spend $11 on the first trip, then the second trip costs $11 + $10 (which is $21).

So we can say in general that if you spend x dollars on the first
trip, then the second trip costs x + 10 dollars.

The third trip costs $10 more than the second trip, and so on. Here
are all the trips:

1st trip: x
2nd trip: x + 10
3rd trip: x + 10 + 10 (which makes x + 20)
4th trip: x + 20 + 10 (which makes x + 30)
5th trip: x + 40
...  
10th trip: x + 90

 

Now we know how much each trip costs, so if we add them up, we get the
total amount. Let's do that:
x + (x + 10) + (x + 20) + (x + 30) + (x+40) + (x + 50) +
(x + 60) + (x + 70) + (x + 80) + (x + 90)
= 10x + 450

But the question says that we had $600 to spend in all. Assuming we
spend it all, then the total we got above (10x + 450) must be $600.

So we write:
10x + 450 = 600

Can you "solve for x" (in other words, find out what value x must have
to make that equation work)?

Hope this helps,
Stephen La Rocque.


 

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