Simple calculation of 25 × (18 + 4)

Simple calculation of 25 × (18 + 4)

25×(18+4)
=25×(4+4+4+4+2+4)
=25×(4×5+2)
=25×4×5+25×2
=100×5+50
=500+50
=550
In order to let the landlord see clearly, the writing is a bit wordy

It is easy to calculate 18 / 25 × 4 + 21 / 25 × 18,

=18/25*4+18/25*21
=18/25*(4+21)
=18/25*25
=18

Simple calculation of 102 * 0.36

=(100+2)×0.36
=100×0.36+2×0.36
=36+0.72
=36.72

36 * 2.54 + 1.8 * 49.2 2004:2003 * 2003 how to calculate easily?
*It's a multiple sign@

Original formula = 1.8 * 50.8 + 108 * 49.2
=1.8*（50.8+49.2）
=1.8*100
==180
2004 = 2003+1