Đáp án:
a) $45$
b) $35,2$
Giải thích các bước giải:
a)
Cách 1:
$\left( 5,28+4,72 \right)\,\,\text{x}\,\,4,5$
$=10\,\,\text{x}\,\,4,5$
$=45$
Cách 2:
$\left( 5,28+4,72 \right)\,\,\text{x}\,\,4,5$
$=5,28\,\,\text{x}\,\,4,5+4,72\,\,\text{x}\,\,4,5$
$=23,76+21,24$
$=45$
b)
Cách 1:
$\left( 7,8-2,3 \right)\,\,\text{x}\,\,6,4$
$=5,5\,\,\text{x}\,\,6,4$
$=35,2$
Cách 2:
$\left( 7,8-2,3 \right)\,\,\text{x}\,\,6,4$
$=7,8\,\,\text{x}\,\,6,4-2,3\,\,\text{x}\,\,6,4$
$=49,92-14,72$
$=35,2$
