Question

S=1.2+2.3+3.4+...+99.100

Hỏi S bằng bao nhiêu?

Answer 1

S = 1.2 + 2.3 +...+ 99.100

3S = 1.2.3 + 2.3.(4 - 1) +...+ 99.100(101 - 98)

3S = 1.2.3 + 2.3.4 - 1.2.3 +...+ 99.100.101 - 98

3S = 99.100.101

3S = 999900

tick nhé

S = 333300

Answer 2

S=1.2+2.3+3.4+...+99.100Hỏi S bằng bao nhiêu?

3S = 1.2.3 + 2.3(4 - 1) + 3.4.(5 - 2) +...+ 99.100.(101 - 98)

3S = 1.2.3 + 2.3.4 - 1.2.3 + 3.4.5 - 2.3.4 +...+ 99.100.101 - 98.100.101

3S = 99.100.101 (Triệt tiêu)

3S = 999900

S = 333300

Answer 3

S = 1.2 + 2.3 + .... + 99.100

3S = 1.2.3 + 2.3.(4-1)  +... + 99.100.(101 - 98)

3S = 1.23 + 2.3.4 - 1.2.3 + ... + 99.100.101 - 98.99.100

3S  = 99  . 100 . 101 = 999900

S = 999900 : 3 = 333300

Answer 4

S=(99.100.101-0.1.2):3=333300