Question

Find the sum of 1,3,7,9,......199

Answer 1

Answer:

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Answer 2

Answer:

$\huge{ \bf \: Sn = 10000 }$

Step-by-step explanation:

$\bf \: here \: A.p. \: series = 1,3,5,7 ,........199 \\ \\ \bf \: \purple {a = 1} \: \: and \: \red d = 3 - 1 = \red2 \: \: \pink{ An =199 } \\ \\ \tt An = a + (n - 1)d \\ \\ \tt \mapsto199 = 1 + (n - 1)2 \\ \\ \tt \mapsto200 = 2n \\ \\ \boxed{\tt \mapsto \: n = 100}\\ \\ \bf \: we \: know \: that \: Sn = \frac{n}{2} \{a + An \} \\ \\ \bf \: Sn = \cancel{\frac{100}{2} }\{1 + 199 \} \\ \\ \bf \: Sn =50 \times 200 \\ \\ \huge{ \bf \: Sn = 10000 }$