计算 percentage change from old 值 to new value:
计算 new 值 from old value and percentage change:
The percentage change from old 值 (Vold) to new 值 (Vnew) is equal to the old and new values difference divided by the old 值 times 100%:
Price percentage increase from old price of $1000 to new price of $1200 is caluclated by:
= 0.2 × 100% = 20%
Price percentage decrease from old price of $1000 to new price of $900 is caluclated by:
= -0.1 × 100% = -10%
The difference d is equal to the old 值 Vold times the percentage change p divided by 100:
The new 值 Vnew is equal to the old 值 Vold plus the difference d:
Vnew = Vold + d
