Question

What is the value of

Answer 1

`\displaystyle\\\sum_(n=2)^6((n-1)!)/(2)=((2-1)!)/(2)+((3-1)!)/(2)+((4-1)!)/(2)+((5-1)!)/(2)+((6-1)!)/(2)=\\\\=(1)/(2)+(2)/(2)+(6)/(2)+(24)/(2)+(120)/(2)=0.5+1+3+12+60=76.5`

Answer 2

D. 76.5

Explanation:

The summation sign means that it is the sum of the expression for all values of n upto 6.

n = 2 below the summation sign means that n starts from 2.

∑(n-1)!/2 from n= 2 to n=6

= (2-1)!/2 + (3-1)!/2 + (4-1)!/2 + (5-1)!/2 + (6-1)!/2

= 1!/2 + 2!/2 + 3!/2 + 4!/2 + 5!/2

= 1/2 + 2*1/2 + 3*2/2 + 4*3*2/2 + 5*4*3*2/2

= 1/2 + 2/2 + 6/2 + 24/2 + 120/2

= 0.5 + 1 + 3 + 12 + 60

= 76.5