Solve the equation for k. -11 = 7 + 2/3k A. -24 B. -25 C. -26 D. -27
1 answer:
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Given:
First term of an arithmetic sequence is 2.
Sum of first 15 terms = 292.5
To find:
The common difference.
Solution:
We have,
First term:
Sum of first 15 terms:
The formula of sum of first n terms of an AP is
Where, a is first term and d is common difference.
Putting , n=15 and a=2 in the above formula, we get
Divide both sides by 15.
Dividing both sides by 7, we get
Therefore, the common difference is 2.5.
We know that
The arrangement forms an isosceles triangle with equal legs of 8 miles.
The angle between the legs is equal to
°
Therefore, the other two angles are
Angles = (180-60)/2 = 120/2 = 60°
It can, therefore, be noted that all angles are equal and thus the resulting triangle is actually an equilateral triangle and thus all the sides are equal.
Hence
the answer is
the distance between the two ships is 8 miles apart
alternative Method
Applying the law of cosines
<span>c²=a²+b²-2*a*b*cos C
</span>where
a=8 miles
b=8 miles
C is the angle between the legs-------> 123-63------> 60 degrees
c is the distance between the two ships
so
c²=8²+8²-2*8*8*cos 60------> c²=64-------> c=√64------> c=8 miles
The arrangement forms an isosceles triangle with equal legs of 8 miles.
The angle between the legs is equal to
Therefore, the other two angles are
Angles = (180-60)/2 = 120/2 = 60°
It can, therefore, be noted that all angles are equal and thus the resulting triangle is actually an equilateral triangle and thus all the sides are equal.
Hence
the answer is
the distance between the two ships is 8 miles apart
alternative Method
Applying the law of cosines
<span>c²=a²+b²-2*a*b*cos C
</span>where
a=8 miles
b=8 miles
C is the angle between the legs-------> 123-63------> 60 degrees
c is the distance between the two ships
so
c²=8²+8²-2*8*8*cos 60------> c²=64-------> c=√64------> c=8 miles