So sánh A với B biết:

$A=\frac{75}{100}+\frac{18}{21}+\frac{19}{32}+\frac{1}{4}+\frac{3}{21}+\frac{13}{32}$

B = (27,5 × 0,1 + 2,5 × 0,1) × 2.

Lời giải:

$A=\frac{75}{100}+\frac{18}{21}+\frac{19}{32}+\frac{1}{4}+\frac{3}{21}+\frac{13}{32}$

$=\frac{3}{4}+\frac{18}{21}+\frac{19}{32}+\frac{1}{4}+\frac{3}{21}+\frac{13}{32}$

$=\left(\frac{3}{4}+\frac{1}{4}\right)+\left(\frac{18}{21}+\frac{3}{21}\right)+\left(\frac{19}{32}+\frac{13}{32}\right)$

B = (27,5 × 0,1 + 2,5 × 0,1) x 2

= [(27,5 + 2,5) × 0,1] × 2

= (30 × 0,1) × 2

= 6

Suy ra A < B (vì 3 < 6).