1. tính nhanh
a) 64,25+35,25+25
=64,25+60,25
=(60,25+4) +60,25
=60,25+4
=64,25
\(a.64\cdot25+35\cdot25+25\)
\(=25\cdot\left(64+35+1\right)\)
\(=25\cdot100\)
\(=2500\)
\(b.58\cdot42+32\cdot58+58\cdot16\)
\(=\) \(58\cdot\left(42+32+16\right)\)
\(=58\cdot90\)
\(=5220\)
BÀI 2
\(890:x=35\left(dư15\right)\)
\(=>\left(890-15\right):x=35\)
\(875:x=35\)
\(x=875:35\)
\(x=25\)
b,c tương tự