1.

The 6th and the 17th terms of an AP are 21 and 54 respectively . The first term of the AP is _?​

Answer» <html><body><p><strong>Answer:</strong></p><p> <a href="https://interviewquestions.tuteehub.com/tag/a6-844638" style="font-weight:bold;" target="_blank" title="Click to know more about A6">A6</a> = 21</p><p>a17 = 54</p><p>an = a +(n-1) d</p><p>a6 = a +(6 - 1) d</p><p>21 = a+ 5d............ (i)</p><p>a17 = a + ( <a href="https://interviewquestions.tuteehub.com/tag/17-278001" style="font-weight:bold;" target="_blank" title="Click to know more about 17">17</a> - 1)d</p><p>54 = a + 16d....(ii)</p><p>by <a href="https://interviewquestions.tuteehub.com/tag/substitution-1231654" style="font-weight:bold;" target="_blank" title="Click to know more about SUBSTITUTION">SUBSTITUTION</a> method,</p><p>21 - 5d = a.........(iii)</p><p><a href="https://interviewquestions.tuteehub.com/tag/substitute-1231629" style="font-weight:bold;" target="_blank" title="Click to know more about SUBSTITUTE">SUBSTITUTE</a> iii in ii</p><p>54 = 21 - 5d + 16d</p><p>54 - 21 = 11d</p><p>33 = 11d</p><p>d = 3</p><p>substitute d in i</p><p>21 = a + 5d</p><p>21 = a + <a href="https://interviewquestions.tuteehub.com/tag/5-319454" style="font-weight:bold;" target="_blank" title="Click to know more about 5">5</a>*3</p><p>21 - 15 = a</p><p>a=6</p><p><strong>therefore the first term of the ap is 6</strong></p><p>AP : 6,9,12,15.......</p><h3>hope it helps you...</h3></body></html>


Discussion

No Comment Found

Related InterviewSolutions