find the ratio of 9th and 7th term of sequence 3.1, 5.6, 8.1, .....?
Choose the correct choice from the following
A) 101/91 B) 181/61 C) 247/194 D) 231/181 E) 408/203
common difference = d = 5.6 - 3.1= 
<gadget id="calculator">5.6 - 3.1</gadget>
<output>2.5</output>
2.5 ,, n= 9, a = first term = 3.1-----   By using arithmetic progression , t9 = a + (n-1)*d = 3.1 + (9-1)*2.5 = 3.1+20= 
<gadget id="calculator">3.1+20</gadget>
<output>23.1</output>
23.1   Also 7th term , t7= a + (n-1)*d = 3.1 + (7-1) * 2.5= 
<gadget id="calculator">3.1 + (7-1) * 2.5</gadget>
<output>18.1</output>
18.1   Ratio= t9/t7 = 23.1/18.1   =231/181 ..... Ans - 231/181
<result>D</result>
find the ratio of 9th and 7th term of sequence 3.1, 5.6, 8.1, .....?