Practical word question

Sep 2016
2
0
New Zealand
Hi. I work out the answer in my head but of course the teacher wants to see my workings! Can someone please show me the equation to use?
Thanks

25 students go to a ball and total amount spent is $5500. Boys spend $100 each and girls spend $400 each. How many girls go to the ball?
 

chiro

MHF Helper
Sep 2012
6,608
1,263
Australia
Hey debtless.

You should show what you have tried and think about it in terms of variables.

To get you started you have three variables here - total amount, amount for boys and amount for girls. Boy and girls amounts are based on number of people and the amount per person.

All up - you have five variables and you have to find some formula that links all of them together in some way.

See if you can go further and tell me how you might try and do that - we can provide assistance if you show your attempts to do so.
 
Sep 2016
2
0
New Zealand
OK so I tried the following but I can't seem to go in the right directions.
1.
5500 = b100 + b400
55 = b500
b = 55/500
b = 0.11

2.
25(b + 4b) = 5500
25b + 100b =5500
125b = 5500
b= 5500/125
b = 44

3.
25(b + (b+300))=5500
b + (b+300) = 5500/25
b + (b+300) = 220
2b + 300 = 220
2b = 220 -300
2b = - 80
b= -40
 

skeeter

MHF Helper
Jun 2008
16,217
6,765
North Texas
25 students go to a ball and total amount spent is \$5500. Boys spend \$100 each and girls spend \$400 each. How many girls go to the ball?
Let $b$ = number of boys

$g$ = number of girls

$b+g=25$

$b(\$100) + g(\$400) = \$5500$


$b=25-g \implies (25-g)(\$100) + g(\$400) = \$5500$

solve for $g$
 
Feb 2015
2,255
510
Ottawa Ontario
Or a shorter route (since you're doing it in your noggin'!):

g = girls : then boys = 25 - g

400g + 100(25 - g) = 5500 : solve for g