The average of marks obtained by 120 boys was 37. If the average of marks of passed boys was 39 and that of failed boys was 15, the number of boys who passed the examination is?  Choose the correct option.
A) 100	B) 110	C) 120	D) 130	E) 140
Let the number of boys who passed = X.   Then, 39 x X + 15 x (120 - X) = 120 x 37   24X = 4440 - 1800   =&gt; X = 2640/24= 
<gadget id="calculator">2640/24</gadget>
<output>110</output>
110.   Hence, the number of boys passed= 110.   ANSWER:110
<result>B</result>
The average of marks obtained by 120 boys was 37. If the average of marks of passed boys was 39 and that of failed boys was 15, the number of boys who passed the examination is?