Four years ago, the average age of a family of 4 members was 21 years.A baby having been born,the average age of the family is the same today.The present age of the baby? Choose the correct option.
A) 5 years B) 7 years C) 2 years D) 3 years E) 6 years
Total age of the 4 members, 4 years ago = (21*4)= 
<gadget id="calculator">(21*4)</gadget>
<output>84</output>
84 years.   Total age of the 4 members now=( 84+ 4*4)= 
<gadget id="calculator">( 84+ 4*4)</gadget>
<output>100</output>
100 years.   Total age of the 5 members now= (21*5)= 
<gadget id="calculator">(21*5)</gadget>
<output>105</output>
105 years.   5 yearsge of the baby is= 105- 100= 
<gadget id="calculator">105- 100</gadget>
<output>5</output>
5 years   5 yearsnswer :5 years
<result>A</result>
Four years ago, the average age of a family of 4 members was 21 years.A baby having been born,the average age of the family is the same today.The present age of the baby?