Question

A "stair-step" figure is made up of alternating black and white squares in each row. Rows $1$ through $4$ are shown. All rows begin and end with a white square. The number of black squares in the $37$ th row is

$34$

$35$

$36$

$37$

$38$

Answer: C

Concepts:pattern recognition basic counting

Difficulty rating: 860

Solution:

Row $n$ contains $2n - 1$ squares. Because both ends are white and the colors alternate, each row has one more white square than black square, so the number of black squares is $n - 1.$

For the $37$ th row, this is $37 - 1 = 36.$

Thus, the correct answer is C .

1985 AMC 8 Problem 7

Answer: C

Solution:

Problem 7 in Other Years