Question

Smith asked daddy to give Rs. $100$ on first day and go no decreasing by Rs. $10$ daily. How much money has he collected in $10$ days?

• A. $550$
• B. $1000$
• C. $480$
• D. $320$

Answer 1

Answer: (A)

$550$

According to question

On first day smith asked daddy to give 100 Rs

and then decrease 10 Rs daily till 10 days

this forms an AP

100,90,80,......10

whose first term [a=100] and [common difference = 10]

now,

sum of P = Total earned by smith = $\frac{n}{2}[2a+(n-1\left)d\right]$

Total sum = $\frac{10}{2}[2\times 100+9\times (-10\left)\right]-[n=10]$

Total sum = $5[200-90]=5\times 110=Rs1550$

Hence Total sum of money collected by smith is 1550 Rs.