## jagatuba 2 years ago Getting from point a to point b: Hattie purchases 3 books for \$3.75 each 5 notepads for \$1.75 each. She uses the following equation to figure the total (before tax): (3 x \$3.75) + (5 x \$1.75) Which of the following is another that could also be used? a. (3 x 5) + (\$ 3.75 x \$1.75) b. (3 + 5) + (\$3.75 x \$1.75) c. (8 x \$3.75) - \$10 d. 15 + (\$3.75 x \$1.75) e. \$3.75 + \$1.75 I know that the correct answer is c just by doing the calculation, what I want to know is how is this equation derived from the data given; what principle(s) are used to come up with (8 x \$3.75) - \$10?

1. Hero

Looks like you already have help

2. asnaseer

note that \$3.75 is exactly \$2 more than \$1.75 so, for every one of the 5 x \$1.75, you can move \$3.75 into the \$3.75 count as longas you reduce the 5 x cost by \$2

3. asnaseer

4. asnaseer

(3 x \$3.75) + (5 x \$1.75) = (3 x \$3.75) + (5 x (\$3.75 - \$2.00))

5. saifoo.khan
6. asnaseer

lol! ^^

7. asnaseer

@jagatuba - did I explain it clearly enough for you?

8. jagatuba

No I'm sorry. I still cannot see how we are getting from (3 x \$3.75) + (5 x \$1.75) to (8 x \$3.75) - \$10 nor what if any mathematical principles are involved.

9. jagatuba

brb

10. asnaseer

ok, do you agree with this step? (3 x \$3.75) + (5 x \$1.75) = (3 x \$3.75) + (5 x (\$3.75 - \$2.00))

11. asnaseer

I don't believe there is any deep mathematical principal being used here - just re-arrangement of monetary amounts to make the calculation easier.

12. asnaseer

you basically need to have noticed that \$3.75 is exactly \$2 more than \$1.75 and that 5 x \$2 is a nice easy calculation

13. asnaseer

you will usually find street merchants are very good at these types of calculations. :)

14. jagatuba

I see thank you for the explanation @asnaseer. Sorry it took so long for me to respond back. I was just getting off work and then went Christmas shopping.

15. asnaseer

np, and yw :)