So
Solution: (1) Indoor area = 4.65× 4.2+5× 6.6+8.4× 5.7 =100.41(square meter).
Stair elevator area =3.9×4.2+3.6×5=34.38 (square meter)
Area undertaken by Mr. Zhang =100.41+34.38÷ 2 =117.6 (square meter)
Total cost =117.6×15000+16× 6000 =1860000 (RMB)-.
(2) If the annual growth rate is x, it is15000 (1+x) 2 = 21600 ∴ x/= 0.2, and x 2 =-2.2 (excluding).
The annual growth rate is 0.2 (or 20%)-6 points.
(3)① If the accumulated shopping does not exceed 5,000 yuan, the shopping consumption amount of the two companies is the same;
(2) If the accumulated shopping exceeds 5,000 yuan and does not exceed 10000 yuan, it will save money by shopping in Company B;
(3) if the accumulated shopping exceeds 10000 yuan, let the accumulated shopping be x yuan (x > 10000).
If the shopping expenses in company A are low, then 5000+0.95 (x-5000) >10000+0.9 (x-100) x >15000.
If the shopping expenses in company B are low, then 5000+0.95 (x-5000) <10000+0.9 (x-100) x <15000.
And when the cost happens to be 15000 yuan, the same amount will be spent in two stores.
Therefore, when the accumulated shopping exceeds 10000 yuan but is less than 15000 yuan, shopping in company b saves money; Cumulative shopping is equal to 15000 yuan, and the consumption amount of the two companies is the same; When the accumulated shopping exceeds 65,438+05,000 yuan, you can save money by shopping in Company A-65,438+00 points.
This topic is related to real life, involving basic calculation, quadratic equation, inequality and other mathematical knowledge. It is very comprehensive.