# The average of six numbers is 30. If the average of first four is 25 and that of last three is 35, the fourth number is: Option 1) Option 2) 50Option 3) Option 4) Option 5)

$Sum \: of\: 6\: numbers = 6*30 = 180$
$A_{1}+ A_{2}+ A_{3}+ A_{4} = 4*25=100 ------(i)$
$A_{4}+ A_{5}+ A_{6} = 3*35=105 ------(ii)$
$Adding (i) \: \: and\: \: (ii)$
$A_{1}+ A_{2}+ A_{3}+ 2A_{4}+ A_{5}+ A_{6}=205$
$A_{4} = 205-180=25$