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Question
Choose the correct alternative answer for the following question .
If for any A.P. d = 5 then t18 – t13 = ....
Options
5
20
25
30
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Solution
It is given that,
d = 5
Now,
\[t_n = a + \left( n - 1 \right)d\]
\[ t_{18} - t_{13} = \left( a + \left( 18 - 1 \right)d \right) - \left( a + \left( 13 - 1 \right)d \right)\]
\[ = \left( a + 17d \right) - \left( a + 12d \right)\]
\[ = 5d\]
\[ = 5\left( 5 \right)\]
\[ = 25\]
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