Question

Find the sum of all two didit odd multiples of 3

Answer 1

$hello \: mate$

The AP will be:

15,21,27...99

an=a+(n-1)d

99=15+(n-1)6

99=15+6n-6

99=9+6n

6n=90

n=15

Now, Sn=n/2(a+l)

So,

Sn=15/2(15+99)

Sn=15/2(114)

Sn=57×15

Sn=855

Answer 2

2d odd multiples of 3

12

15

18

21

24

27

30

33

36

39

42

45

48

51

54

57

60

63

66

69

72

75

78

81

84

87

90

93

96

99

Sum=9387