## dannielle 3 years ago At the end of the first day, 7 weeds appear in your neighborhood park. Each day, the number of weeds increases by four times. How many weeds will be in the park at the end of 14 days?

1. mia0bbb

7 weeds x 4 x 14 days

2. lilg132

7 + (14 - 1) * 4

3. lilg132

59 weeds in the park at the end of 14 days

4. dannielle

it cant be, the answer choices are 71 626,349,395 392 35,456,231

5. mia0bbb

6. mia0bbb

because 7 x 4 x 14 = 392

7. lilg132

oh wait we need to work out the sum

8. dannielle

yeah, but im feeling there is a formula to it or something, my teacher wouldnt make it that easy

9. mia0bbb

14( 7 x 4 )

10. lilg132

11. lilg132

i'm not sure of the formula but what i do know is we have 7 weeds on the first day and it multiplies by 4 each day and you do it 14 times and add all the figures up giving you 626349395

12. dannielle

alright, that does make sense, thank you !

13. lilg132

your welcome i will try and look for the formula for you

14. dannielle

thank you (:

15. mathmate

Use the compound interest formula: 7(4^14-1)/(4-1)=626349395 which is equivalent to 7(1+4+4^2+...4^13)

16. lilg132

thats what i was looking for :)