Question

Tinas puppy ate 100 dog biscuits on the first five days since she got it. if each day her puppy had eaten 6 more than the previous day, how many biscuits had it eaten on the first day?

Answer 1

Sn=n/2[2a+(n-1)d]
100=5/2[2a+(5-1)6]
200-24=10a
176=10a
a = 176/10
a=17.6 biscuits the dog ate on the first day.

Answer 2

Answer:

The first day the puppy ate 8 biscuits.

Solution:

Assume that the puppy ate ‘a’ number of biscuits on the first day.

Every day he ate 6 more than the previous day. So, the common difference between every day d=6.

On first five days dog ate 100 biscuits, so $S_{5}=100$

$a+(a+d)+(a+2 d)+(a+3 d)+(a+4 d)=100$

$5 a+10 d=100$

$a+2 d=20$

$a=8$

So the first day the puppy ate 8 biscuits.