Giải thích các bước giải:
B1:
a,2/3=2x4/3x4=8/12; 3/4=3x3/3x4=9/12
b,9/4=9x5/4x5=45/20; 3/5=3x4/5x4=12/20
c,2/5=2x7/5x7=14/35; 4/7=4x5/7x5=20/35
d,3/5=3x3/5x3=9/15; 4/3=4x5/3x5=20/15
B2:
a,3/12+1/4=3/12+1x3/1x4=3/12+3/12=6/12
b,4/25+3/5=4/25+5x3/5x5=4/25+15/25=19/25
c,26/81+4/27=26/81+4x3/27x3=26/81+12/81=38/81
d,5/64+7/8=5/64+7x8/8x8=5/64+56/64=61/64
B3:
Sau 2 giờ oto đó chạy được số phần quãng đường là:
3/8+2/7=21/56+16/56=37/56