Question

Ex. (•) Anvar saves some amount every month. In first three months he saves
* 200, * 250 and 300 respectively. In which month will he save * 1000?​

Answer 1

Answer:

hhhbbnnnnnnjjjjjjjnnnn

Answer 2

Answer:

Saving in first month ₹200; Saving in second month ₹250;...200,250,300. (this is an A.P)

$\sf \: Here \: A=200, \: d=50, \\ \\ \: \sf \: \pink{Let's \: find \: using \: t_n}$

$\sf \: Formula \: and \: then \: find \:s_n$

$\sf \: t_n=a+(n-1)$

$\sf \: =a+(n−1)d$

$\begin{gathered}\sf \implies \: \sf200 + (n - 1) - 50 \\ \\ \sf = 200 + 50n - 50 \\ \\ \sf \: 1000 = 150 + 20n\end{gathered}$

$\begin{gathered}\sf \implies \: 150n + 50n = 1000 \\ \\ \sf \: = 50n = 1000 - 150 \\ \\ \sf \: = 50n = 850 \\ \\ \sf \therefore \: n = 17\end{gathered}$

$\red{ \sf \: In \: the \: 17 {}^{th} \: month \: he \: will \: save \: ₹1000}$

Let's find that in 17 month how much total amount is saves.

$\begin{gathered}\sf \implies \sf \: s_n = \frac{n}{2} \: \: \: \: \: \: \: \: \: \: \bigg[2a + (n - 1)d \bigg] \\ \\ = \sf \: \frac{17}{2} \: \: \bigg[2 \times 200 + (17 - 1) \times 50\bigg] \\ \\ \sf = \frac{17}{2} \: \: \: \bigg[400 + 800\bigg] \\ \\ \sf \: \sf \implies17 \times 600 \\ \\ \sf \pink{= 10200}\end{gathered}$

Hence, In 17 months total saving is ₹10200.