The bottom and height of a parallelogram are reduced by a ratio of 1:3. What is the area after reduction?

The bottom and height of a parallelogram are reduced by a ratio of 1:3. What is the area after reduction?

The base and height of a parallelogram are reduced by a ratio of 1:3, and the reduced area is 1 / 9 of that before reduction
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1.36 times 4 times 2.5 = simple calculation

1.36 * (4*2.5) = 1.36*10 = 13.6

For rational number AB, we define a new algorithm as a & B = AB / 1-ab, for example: 3 & 2 = 1-3 * 2 / 3 * 2 = 1-6 / 6 = - 5 / 6
①5&（-3）②（1&4）&1/5

5&（-3）=[5×（-3）]/[1-5×（-3）]=-15/16
（1&4）=(1×4）/(1-1×4）=-4/3
（1&4）&1/5=(-4/3)&1/5=(-4/3×1/5)/[1-(-4/3)×1/5]=-4/19