Sender: Angie Herbert
Subject: algebra
Hi
My daughter is having problems with her algebra homework. She is a year 7 pupil at high school in the UK. She has been given homework on simplifying formulae and she doesn't understand how to do them. Here is an example of one of the questions :
9s+7t+5c+5s3t
can you help her to understand how to do these and perhaps me too.
Thanks
puzzled mum
Angela Herbert
Hi Angela,
Simplifing this expression (some teachers may use the expression "collecting like terms") involves gathering all the s's, all the t's and all the c's. There are 9 s's and a further 5 s's so altogether 9+5=14 s's. Likewise there are 7 t's from which you remove 3 t's leaving you with 73=4 t's. To say it properly
9s + 7t + 5c + 5s  3t
= 9s + 5s + 7t  3t + 5c
= (9 + 5)s + (7  3)t + 5c
= 14s + 4t + 5c
Penny
Here is another approach.
 Give meaning to the variables (for instance s: steaks,
t: tomatoes, c: carrots
 Rewrite the equation in this meaningful way:
9 steaks + 7 tomatoes + 5 carrots + 5 steaks  3 tomatoes
 Rewrite the above in a simpler way:
14 steaks + ...
 Remove the meaning of the variables (put back s for steaks,
t for tomatoes and c for carrots).
Claude
Go to Math Central
