Question

Tính nhanh: a) ( 68 x 72 x 49) x ( 27 x 12 – 9 x 36 )

b) ( 25 x 50 – 125 x 10 ) x ( 1 + 2 + 3 + ……….. + 99 + 100

 

Answer 1

a: \(=68\cdot72\cdot49\cdot\left[324-324\right]=0\)

b: \(=\left(1250-1250\right)\cdot\left(1+...+100\right)=0\)

Answer 2

\(a,\left(68\times72\times49\right)\times\left(27\times12-9\times36\right)=\left(68\times72\times49\right)\times0=0\\ b,\left(25\times50-125\times10\right)\times\left(1+2+...+100\right)=0\times\left(1+2+...+100\right)=0\)

Answer 3

a, ( 68 × 72 × 49 ) × ( 27 × 12 − 9 × 36 ) = ( 68 × 72 × 49 ) × 0 =

b, ( 25 × 50 − 125 × 10 ) × ( 1 + 2 + ... + 100 ) = 0 × ( 1 + 2 + ... + 100 ) = 0

Answer 4

\(1+2+3+...+99+100.\)

Số số hạng: \(\left(100-1\right):1+1=100.\)

Tổng số số hạng:

\(\dfrac{\left(100+1\right)\times100}{2}=5050.\)

\((25\times50-125\times10)\times(1+2+3+...+99+100).\)

\(=\left(125\times10-125\times10\right)\times5050=0.\)