Question

Mong các bạn trả lời nhanh nhanh nha:

Bài 1:

a.1+3+5+7+…+90

b.2+4+6+84+…+98

c.11+12+13+14+…+50

Answer 1

a) 1 + 3 + 5 + 7 + ...+ 91

= (1+91) x [(91-1):2+1] : 2

= 2116

b) 2 + 4 + 6 + 8 + ... + 98

= (98+2) x [(98-2):2+1]:2

= 100 x 49 : 2

= 50 x 49

= 2450

c) 11 + 12 + 13 + ...+ 50

= (50+11) x [(50-11):1+1] : 2

= 1220

Answer 2

sai 1 chỗ nha bạn 11+12+13+14 chứ 

Answer 3

\(=\left[\left(91-1\right):2+1\right].\left(90+1\right):2\)

\(=46.91:2\)

\(=2093\)