Question

If 4,a,b,c,28 are in AP,then c=? * 1 point

Answer 1

$Given \: 4,a,b,c,28 \:are \: in \: AP.$

$First \:term (a) = 4 \: --(1)$

$Fifth \:term (a_{5}) = 28$

$\implies a + 4d = 28$

$\boxed{ \pink{ n^{th} \:term (a_{n}) = a+(n-1)d }}$

$\implies 4 + 4d = 28 \: [ From \: (1) ]$

$\implies 4d = 28 - 4$

$\implies d = \frac{24}{4}$

$\implies d = 6\: --(2)$

$Now , c = a_{4}$

$\implies c = a + 3d$

$\implies c = 4 + 3 \times 6 \: [ From \:(1) \:and \:(2)$

$\implies c = 4 + 18$

$\implies c = 22$

Therefore.,

$\red{ Value \: of \: c } \green { = 22 }$

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