two pipes a and b can fill a cistern in 10 and 15 minutes respectively. both fill pipes are opened together, but at the end of 3 minutes, ‘ b ’ is turned off. how much time will the cistern take to fill? Select.
A) 6 min
B) 8 min
C) 10 min
D) 12 min
E) none of these
<gadget id="calculator">1 / 10</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/10) + (1/15)</gadget>
<output>1/6 = around 0.166667</output>

<gadget id="calculator">(1/6) * 3</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (1/2)</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">10 * (1/2)</gadget>
<output>5</output>

<gadget id="calculator">5 + 3</gadget>
<output>8</output>

<result>B</result>
two pipes a and b can fill a cistern in 10 and 15 minutes respectively. both fill pipes are opened together, but at the end of 3 minutes, ‘ b ’ is turned off. how much time will the cistern take to fill?
add(multiply(10, subtract(const_1, multiply(add(inverse(10), inverse(15)), const_3))), 3)
in one min , ( a + b ) fill the cistern = 1 ⁄ 10 + 1 ⁄ 15 = 1 ⁄ 6 th in 3 min , ( a + b ) fill the cistern = 3 ⁄ 6 = 1 ⁄ 2 th remaining part = 1 - 1 ⁄ 2 = 1 ⁄ 2 ∵ 1 ⁄ 10 th part filled by a in one min . ∴ 1 ⁄ 2 nd part filled by a in 10 × 1 ⁄ 2 = 5 min . ∴ total time = 3 + 5 = 8 min . answer b