Foil it out:
(7x)(4x)+(7x)(9)+(-8)(4x)+(-8)(9)
28x^2+63x-32x-72
28x^2+31x-72
Answer:
Read below.
Step-by-step explanation:
Wrong:
(2.5 x 10^9) + (5.3 x 10^8) =
(2.5 + 5.3) x (10^9 x 10^8)
=
7.8 x 10^7=
7.8 x 10,000,000=
780,000,000
<u>Bold is edited by me</u>
Correct:
(2.5 x 10^9) + (5.3 x 10^8)=
(2.5 x 1,000,000,000)+(5.3 x 100,000,000)=
2,500,000,000+5,300,000,000=
7,800,000,000
The problem is that whoever wrote it swapped the numbers in the parentheses, added a pair of them together and multiplied the other pair. You are not supposed to take out the pairs and swap them if you'd like or the answer is incorrect. Second mistake is that
is not
I do not know how and where you got that answer from.
We know that
l² = r² + h²
l² = (10.5)² + (36)²
l² = 110.25 + 1296
l² = 1406.5
l = √(1406.5)
l = 37.5 cm
Now,
CSA of cone = πrl
=> 22/7 × 10.5 × 37.5
=> 22 × 1.5 × 37.5
=> 1237.5 cm²
Area of 20 caps = 20 × 1237.5
=> 24750 cm²