## anonymous one year ago Help please....... A computer can perform c calculations in s seconds. How many minutes will it take the computer to perform k calculations? a. 60ks/c b. ks/c c. ks/60c d. 60c/ks e. k/60cs

1. anonymous

60 sec in 1 min so i think its not b

2. anonymous

i know the answer i want to know how to do it.

3. mathstudent55

The speed of calculations is: $$speed ~of~ calculations = \dfrac{calculations}{time}$$ $$speed ~of~calculations = \dfrac{c}{s} \dfrac{calculations}{second}$$ $$time = \dfrac{calculations}{speeedd~of~calculations}$$ $$\dfrac{1 ~minute}{60 ~seconds} = 1$$ $$time = \dfrac{k~calculations}{\frac{c~calculations}{s~seconds}} = \dfrac{ks}{c} seconds \times \dfrac{60~seconds}{1~minute} = \dfrac{60ks}{c} per ~minute$$

4. phi

***A computer can perform c calculations in s seconds. How many minutes will it take the computer to perform k calculations?**** we are given a rate c calcs per s seconds rate*time = amount so $\frac{c \ calcs}{s \ secs} \cdot t = k \ calcs$ solve for t $t = \frac{k\ s \ secs}{c}$ that is the time in seconds. if we mutliply by 1 minute/60 secs $t = \frac{k\ s}{c} \ \cancel{seconds} \cdot \frac{1 \ minute}{60 \ \cancel{seconds}}\\ t= \frac{k s}{60c} \ mins$

5. phi

mathstudent messed up the conversion from seconds to minutes.

6. anonymous

Is that a formula? The speed of calculations thing he mentioned?

7. phi

rate * time = distance is a formula you learn to figure out how far you go at a given speed. but many problems are similar to this, and can use the same idea when I see amount per time I think "rate" and see if rate * time = amount makes sense. (It usually does)

8. anonymous

ohh okay i see

9. anonymous

|dw:1440458170535:dw|

10. anonymous

i got that far

11. anonymous

i don't understand from there to be honest

12. phi

what does "x" represent in your ratio?

13. anonymous

# of calculations per minute

14. phi

good. so x is a rate: calculations per minute so use rate * time = amount we know the rate. we are given an amount (k) so we can find time , and it will be in minutes.

15. anonymous

ohhhhhh okay got it

16. phi

it takes practice to think "clearly". Lots of practice.

17. anonymous

yea lots of practice ^_^ thanks phi!!

18. mathstudent55

@phi Thanks for pointing it out. $$time = \dfrac{k~calculations}{\frac{c~calculations}{s~seconds}} = \dfrac{ks}{c} \cancel{seconds} \times \dfrac{1~minute}{60~\cancel{seconds}} = \dfrac{ks}{60c} ~minute$$

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