Đáp án:
a) 18 + 15 + 22 + 45
$=$ $\text{ ( 18 + 22 ) + ( 15 + 45 )}$
$=$ $\text{ 40 + 60 }$
$=$ $100$
b) 276 + 118 + 324
$\text{= ( 276 + 324 ) + 118}$
$\text{= 600 + 118 }$
$=$ $718$
c) 5. 9. 3. 2
$\text{ = ( 5 . 2 ) .3 .9}$
$=$ $10$ $.3$ $.9$
$=$ $270$
d) 25. 5. 4. 27. 2
$\text {= ( 25.4 ) . (5.2 ) . 27}$
$=$ $100$.$10$.$27$
$=$ $27000$
Giải thích các bước giải: