Question

520 logs are stacked and arranged. the bottom row contains 45 logs. No of logs go on decreasing by 2 successive upper rows. How many rows are there? What is no of logs in top row? Can u arrange 225 logs in this way?

Answer 1

Answer:

Step-by-step explanation:

So the sequence of arranging logs id 45 43 41...

This is an ap with d=-2 and a=45

For 520 logs

520=sum of ap till n terms(n is number of rows)

520=n(90-2(n-1))/2=n(46-n)

=>n^2 -46n+520=0

=>(n-26)(n-20)=0

n=20

Not 26 as to go till we would have to take -ve number of logs

Lets assume we can take 225 logs so

225=n(46-n)

n^2 -46n+225=0

D of the equation=46^2 - 4*225=1216

Which not a perfect square

So we can arrange 225 logs in this way but we would fall short of logs for the last row

Answer 2

Answer:

520 logs are selected and arranged as shown in the fig. The bottom

row contains 45 logs. Number of logs go on decreasing by 2 in

successive by 2 in successive upper rows. How many rows are there?

What is the number of logs in the top row? Can you arrange 225 logs

in this way?