谁来帮我解决这三道数学题?

题目

谁来帮我解决这三道数学题?
用简便计算：10.5÷3.5÷3 4.2×9.1+42×0.09 16×0.25

答案

10.5÷3.5÷3
=10.5÷(3.5×3)
=10.5÷10.5
=1
4.2×9.1+42×0.09
=4.2×9.1+4.2×0.9
=4.2×(9.1+0.9)
=4.2×10
=42
16×0.25
=4×4×0.25
=4×(4×0.25)
=4×1
4