Saved Bookmarks
| 1. |
In an A.P. the fifth term and tenth term are in the ratio of 1:2 if T12=36 find A.P.\xa0 |
| Answer» Let first term of AP = aCommon difference = dThenT12= a + (12-1)d=> 36 = a + 11d .....(1)Also{tex}{T_5\\over T_{10}} = {1\\over 2}{/tex}=>\xa0{tex}{a+4d\\over a+9d}={1\\over 2}{/tex}=> 2a+8d = a+9d=> a = d ...(2)Put a = d in (1) we get=> 36 = d + 11d=> 36 = 12d=> d = 3From (2) a = 3AP : 3,6,9,12,15 | |