Diketahui:
Ditanya:
S45
Penyelesaian:
Cari beda (b) :
a + 7b = 240
a + 18b = 295
------------------- -
-11b = -55
b = -55/-11
b = 5
.
Cari suku pertama (a) :
a + 7(5) = 240
a + 35 = 240
a = 240 - 35
a = 205
Tentukan S45 :
Sn = n/2 (2a + (n - 1)b)
S45 = 45/2 (2(205) + (45 - 1)5)
S45 = 22,5(410 + 220)
S45 = 22,5(63)
S45 = 14.175
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Diketahui:
Ditanya:
S45
Penyelesaian:
Cari beda (b) :
a + 7b = 240
a + 18b = 295
------------------- -
-11b = -55
b = -55/-11
b = 5
.
Cari suku pertama (a) :
a + 7b = 240
a + 7(5) = 240
a + 35 = 240
a = 240 - 35
a = 205
.
Tentukan S45 :
Sn = n/2 (2a + (n - 1)b)
S45 = 45/2 (2(205) + (45 - 1)5)
S45 = 22,5(410 + 220)
S45 = 22,5(63)
S45 = 14.175