Observe the following patterns. Then find the sum of 1+3+5+7+9+...+19. 1 \[=1\times 1=1\] 1+3 \[=2\times 2=4\] 1+3+5 \[=3\times 3=9\] 1+3+5+7 \[=4\times 4=16\] 1+3+5+7+9 \[=5\times 5=25\]

Observe the following patterns. Then find the sum of 1+3+5+7+9+...+19.

1.	Observe the following patterns. Then find the sum of 1+3+5+7+9+...+19. 1 \[=1\times 1=1\] 1+3 \[=2\times 2=4\] 1+3+5 \[=3\times 3=9\] 1+3+5+7 \[=4\times 4=16\] 1+3+5+7+9 \[=5\times 5=25\]
A.	121
B.	81
C.	100
D.	64
Answer» D. 64