Answer:
90
Step-by-step explanation:
The first term = 6* 2^0 = 6
The second term = 6 * 2^ (2-1) = 6*2 = 12
The third term = 6* 2^(3-1) = 6*2^2 = 6*4 = 24
The fourth term = 6* 2^(4-1) = 6* 2^3 = 6*8 = 48
S4 is the sum of the 1st four terms
S4 = 6+ 12+24+ 48 = 90
17. Area of triangle: 1/2bh
1/2 * 12 * 15
1/2 * 180
=90 cm^2
18. Area of trapezoid: 1/2 h (b1 + b2)
1/2 * 8 ( 12 + 15.4)
4 * 27.4
= 109.6 cm^2
