Question

(20/21)+(20/21)2+(20+21)3

Answer 1

.95+1.905+123=125.855

Answer 2

20/21 + (20/21)^2 + ( 20/ 21 )^3

= 20/21 + 400/441 + 8000 / 9261

= 2.72

OR

also find this sum by LCM method

take the LCM of denominator = 9261 ( because that is the largest number and all are the multiples of 21 )

and make the denominator 9261 in all terms

20/21 [ multiply numerator and  denominator by 441 to make its denominator 9261 ]

20*441 / 21 * 441 = 8820 / 9261

400* 21 / 441 * 21 = 8400 / 9261

8000 * 1 / 9261 * 1 = 8000 / 9261

( 8820 / 9261 )+( 8400 /9260 ) + ( 8000 / 9261 )

25220 / 9261 = 2.72