Question

The average of the weights of six people sitting in a boar is 145 pounds. After a seventh person gets into the boat, the average of the weights of all seven people in the boat is 147 pounds. What is the weights ( in pounds ) of the seventh person ?
a) 160, b) 159, c) 155, d) 149, e) 147

Answer 1

Weight : 

⇒ x for 6 people
⇒ y for the 7th person

$x/6=145 \\ (x+y)/6=147 \\ \\ x=145*6 \\ x=870 \\ \\ x+y=1029 \\ \\ 870+y=1029 \\ y=1029-870 \\ y=159$

The correct answer is B).

Answer 2

X - weight of six people
y - weight of 7th person

$\frac{x}{6}=145\\ \frac{x+y}{7}=147\\\\ x=870\\ x+y=1029\\\\ 870+y=1029\\ y=159\ lb\Rightarrow B$