Pyramid cut

We cut the regular square pyramid with a parallel plane to the two parts (see figure). The volume of the smaller pyramid is 20% of the volume of the original one. The bottom of the base of the smaller pyramid has an area of 10 cm2. Find the area of the original pyramid.

Correct answer:

S1 =  29.2402 cm2

Step-by-step explanation:

S2=10 cm2 S2  = a22 a2=S2=10=10 cm3.1623 cm  V2 = 10020 V1  31 S2 h2 = 10020 31  S1 h1  S2 h2 = 0.20 S1 h1  a1:h1 = a2:h2 a1:a2 = h1:h2  S2 = a1/a2   0.20 S1 a23 = a13   0.20  a1 = ( a23 / 0.20 ) 1/3 a1=a2 31/0.20=3.1623 31/0.205.4074 cm  S1=a12=5.40742=29.2402 cm2



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