How many poles will there be in a stack of telephone piles if there are 58 in the first layer, 57 in the second, 56 in the third, and so on, with 12 in the top layer?

1,645 poles

Step-by-step explanation:

Here, we want to calculate the total number of poles

We can have an arithmetic progression here

Where the last term is the 58 piles , the first term is the top layer which is 12 and the common difference between the piles is 1

Firstly, we calculate the number of stacks which can be obtained using the nth term formula;

Tn = a + (n-1)d

58 = 12 + (n-1)1

58 = 12 + n - 1

58 = n + 11

n = 58-11

n = 47

So we have the stack high up to 47 units

So, using the sum of terms in an arithmetic sequence formula, we have;

Sn = n/2 ( a + L)

where a is the first term 12 and L is the last term 58

Thus, we have

Sn = 47/2( 12 + 58)

Sn = 47/2 * 70

Sn = 1,645

if x decreases by 4 then y increases by 10

step-by-step explanation: