Question

Ahmed has a recurring deposit account in a bank.He deposits Rs $5,500$ per month for 2 years.If he gets Rs $1,46,437.5$ at the time of maturity. Find the interest paid by the bank.

• A. $10.5$%
• B. $30$%
• C. $35$%
• D. None of the above

Answer 1

The correct option is A $10.5$%

Given:

$PQR$ is tangent at $Q$.

$O$ is the center of the circle.

Hence, $OQ$ is perpendicular to $PQR$ (Line passing through center is perpendicular to tangent)

$\angle OQR=90°$

$\angle SQR=50°$

$\angle SQO=\angle OQR-SQR=40°$

Similarly,

$\angle OQT=90°-70°=20°$

$OQ=OS$ (radius of the circle)

hence, $\angle SQO=\angle OSQ=40°$ (angles opposite to equal sides are equal)

Hence $\angle TQS=\angle SQO+\angle OQT=60°$

In $△OQS$

$\angle QOS=180-\angle SQO-\angle OSQ=180°-40°-40°=100°$

$\angle QTS=\frac{\angle QOS}{2}=50°$ (Angle subtended at center is twice the angle subtended on the circumference)

In $△TSQ$

$\angle TSQ=180°-\angle SQT-\angle STQ=x+\angle OSQ$

$x+40°=180°-60°-50°$

$x+40°=70°$

$x=30°$