IDNStudy.com, ang iyong gabay para sa malinaw at eksaktong mga sagot. Anuman ang kahirapan ng iyong mga tanong, ang aming komunidad ay may mga sagot na kailangan mo.

How do you answer this arithmetic progression question?

If a boy saved P(Peso)25 on the first day,P27 the second day,P29 the third day,and,so on, How many days will it take him to save P880?

Sagot :

This is the formula for the sum of an arithmetic series
[tex] \frac{n}{2} [2 a_{1} +(n-1)d][/tex] (d is for the difference and n is for the number of terms)
We substitute  the values
[tex] \frac{n}{2} [50+(n-1)2] = 880 [/tex]
[tex] \frac{n}{2} [50+2n-2] [/tex]
[tex] \frac{n}{2} [48+2n][/tex]

[tex]1760=n[48+2n][/tex]
[tex]1760=48n+ 2n^{2} [/tex]
[tex]0=48+ 2n^{2} -1760[/tex]
[tex]0=(2n+88)(n-20) [/tex]

[tex]2n+88=0 [/tex]
[tex]2n=-88[/tex]
[tex]n=-44[/tex]
which is not possible

[tex]n-20=0[/tex]
[tex]n=20[/tex]

Therefore it will take 20 days