It'd be easier to do #18 if y ou were to break it up:
14* (first term + 14th term)
Sum from n=1 to 14 of n = S = ---------------------------------
14 2
14(1+14)
= ---------------- = 7(15) = 105
2
The sum of twice that is 210. The sum of "1 from n=1 to n=14" is just 14.
The final sum is 210 + 14 = 224 (answer)
1. 24 students and 3 absent
24-3=21
so 21 student goes
2. 21 students divided by the 3 vans
equals to 7
so 7 student went in each van
We are given an isosceles triangle.
An isosceles triangle has corresponding angles of corresponding sides same.
<em>Therefore, other angle is also of (3x+7) degrees.</em>
(5x+13) and (3x+7) makes a linear pair.
Therefore,
(5x+13) + (3x+7) = 180
5x +13 + 3x +7 = 180.
8x +20 = 180.
Subtracting 20 from both sides, we get
8x +20-20 = 180-20.
8x = 160
Dividing both sides by 8, we get
<h3>x = 20.</h3><h3>Therefore, correct option is 3rd option. </h3>
