2.8×4+7.2÷0.25
=2.8×4+7.2÷1/4
=2.8×4+7.2×4
=(2.8+7.2)×4
=10×4
=40
126.5÷0.25÷40
=126.5÷(0.25×40)
=126.5÷10
=12.65
5.13×0.27+2.7×0.513
=5.13×0.27+5.13×0.27
=2×5.13×0.27
=10.26×0.27
=(10+0.2+0.06)×0.27
=10×0.27+0.2×0.27+0.06×0.27
=2.7+0.054+0.0162
=2.7702