Question

840 logs of wood are placed in 7 rows one above the other. The bottom row consists of maximum logs. Each of the subsequent rows consists of 30 logs less than the previous row . Find the number of logs in each row

Answer 1

210,180,150,120,90,60,30.

Step-by-step explanation:

Let the number of logs in first row be = x

No. of rows = 7

Difference in logs of each row = (-30)

This becomes an arithmetic progression,

where a = x ; d = (-30) ; n = 7 ; Sₙ = 840

Now by using the formula for finding the sum of 'n' terms of an A.P., we get,

Sₙ = n/2 x {2a + (n-1)d}

840 = 7/2 x {2x + 6(-30)}

840(2)/7 = 2x - 180

(240 + 180)/2 = x

210 = x

Hence the number of loge in each row were 210,180,150,120,90,60,30.

Hope it helps you....

$<marquee scrollamount = 500>ItzHarsh★</p><p><marquee>$

Answer 2

Hey Mate Here Is ur Answer.....

210,180,150,120,90,60,30.

Step-by-step explanation:

Let the number of logs in first row be = x

No. of rows = 7

Difference in logs of each row = (-30)

This becomes an arithmetic progression,

where a = x ; d = (-30) ; n = 7 ; Sₙ = 840

Now by using the formula for finding the sum of 'n' terms of an A.P., we get,

Sₙ = n/2 x {2a + (n-1)d}

840 = 7/2 x {2x + 6(-30)}

840(2)/7 = 2x - 180

(240 + 180)/2 = x

210 = x

Hence the number of loge in each row were 210,180,150,120,90,60,30.