Quandaries and Queries
 

 

Hi! I'm Dimitri, a middle school student. I am doing very well in math but i just can't figure this question out. A boat weighs 1500 lb more than its motor and 1900 lb more than its trailer. Together the boat and motor weigh five times as much as the trailer. How much does the boat weigh? If you could help, i'd be great
 

 

Hi Dimitri,

I would use a letter for each of the weights and write down equations for each of the statements. The equations may be easier to analyze than the english.

Let B be the weight of the boat, T the weight of the trailer and M the weight of the motor.

A boat weighs 1500 lb more than its motor, becomes
B = M + 1500

A boat weighs 1900 lb more than its trailer , becomes
B = T + 1900

Together the boat and motor weigh five times as much as the trailer
B + M = 5 T

The third equation has all three variables in it and the first two have two variables each with B in both of the first two equations. I can subtract 1500 from both sides of the first equation to get

M = B - 1500

Likewise I can subtract 1900 from both sides of the second equation to get

T = B - 1900

Now if I use these last two equation and replace M and T in the third equation I have an equation in B alone. That is

B + M = 5 T, so
B + (B - 1500) = 5 (B - 1900)

Can you now solve this equation for B?

Penny