Compose an expression to find the 20th term of any arithmetic sequence in terms of just a and d. Look at the pattern in part A with the first three terms to help you.
20th term:

Hello,

Step-by-step explanation:

u(i) is the ith term of the a.s

a is the first term and d the common difference

for n in {1,2,3...}: u(n)=a+(n-1)*d

u(1)=a+0*d=a

u(2)=u(1)+d=a+d=a+1*d

u(3)=u(2)+d=a+1*d+d=a+2*d

...

u(20)=a+19*d

1.8 km

Step-by-step explanation:

The scale on the map is 1 : 15000.

This means that every 1 cm on the map is equal to 15000 cm on the ground.

12 cm on the map will therefore be:

12 * 15000 = 180000 cm

Let us convert to kilometres:

100000 cm = 1 km

180000 cm = 180000 / 100000 = 1.8 km

12 cm on the map will be 1.8 km on the ground.