Use the Appropriate Formula to Find the Indicated Figurate Number $\mathrm { S } _ { 8 } = 36$

Multiple Choice

Use the appropriate formula to find the indicated figurate number.
-the 8th square number

A) $\mathrm { S } _ { 8 } = 36$
B) $\mathrm { S } _ { 8 } = 64$
C) $\mathrm { S } _ { 8 } = 81$
D) $\mathrm { S } _ { 8 } = 16$