Slot method
20 options
3 slots
First slot: 20 options
Second slot: 19 options (one used up for 1st slot)
Third slot: 18 (one less than last)
Multiply them
20 times 19 times 18=6840
Answer is 6840 ways
Multiplying fractions 12x5/9= The Answer Is 20/3
So product means multiply
les than means minus
product of 18 and 5 less than a number means
18 times (x-5)
is 162
equals
18(x-5)=162
divide both siddes by 18
x-5=9
add 5
x=14
Okay what’s your question
The sum of the arithmetic sequence given by
<span>an = 0.05(n – 1) – 0.6
will be given by:
a1=0.05(1-1)-0.6=-0.6
a2=0.05(2-1)-0.6=-0.55
a3=0.05(3-1)-0.6=-0.5
a4=0.05(4-1)-0.6=-0.45
a5=0.05(5-1)-0.6=-0.4
thus the summation will be:
-0.6+(-0.55)+(-0.5)+(-0.45)+(-0.4)
=-2.5
hence
S5=-2.5</span>
