SOLUTION: In a typical group of 1000 workers from each of the boatbuilding, iron foundry, and amusement park/arcade industries, there were 30 more injuries in iron foundries (I) than in amus

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Question 723929: In a typical group of 1000 workers from each of the boatbuilding, iron foundry, and amusement park/arcade industries, there were 30 more injuries in iron foundries (I) than in amusement parks/arcades (A). There were 12 more injuries in amusement parks/arcades than in boatbuildings (B). Among these workers, there were 387 nonfatal occupational injuries. How many injuries took place in each industry?
I'm guessing (keyword being guessing) that:
Data:1000 workers, I had 30 more than A and A had 12 more than B and the total is 387.
Variable: A= amusement parks/arcades, B= boatbuildings, I= iron foundry
Plan: B+(B+A)+(B+I)= 387
Equation: B+(B+12)+(B+30)=387
3B+42 = 387
-42 -42
3B = 345
3B/3 345/3
B = 115
Solution: A= 127, B= 115, and I= 145
Am I right?

Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

there were 387 nonfatal occupational injuries
let the boat-building injuries be B,amusement park/arcade injuries be A, and iron foundry injuries be I
given:
B%2BA%2BI=387
A=B%2B12
I=A%2B30...substitute A ...=> I=B%2B12%2B30...=> I=B%2B42
B%2BA%2BI=387...plug in all values
B%2B%28B%2B12%29%2B%28B%2B42%29=387...solve for B
3B%2B12%2B42=387
3B%2B54=387
3B=387-54
3B=333
B=333%2F3
highlight%28B=111%29
now find A and I
A=B%2B12
A=111%2B12
highlight%28A=123%29

I=B%2B42
I=111%2B42
highlight%28I=153%29
check their sum:
B%2BA%2BI=387
111%2B123%2B153=387
387=387
check your solution: A= 127, B= 115, and I= 145
Am I right?
your equation: B%2B%28B%2B12%29%2B%28B%2B30%29=387 ...you put I=%28B%2B30%29, but it is given that I had 30 more than A, or I=A%2B30
so, you need to put

B%2BA%2B%28A%2B30%29=387
since also given that A had 12 more than B, we know that A=B%2B12 and we go back to I and substitute A
I=A%2B30...=>...I=B%2B12%2B30=B%2B42
now, plug it in equation
B%2B%28B%2B12%29%2B%28B%2B42%29=387