Chapter 4 - Number Representation and Calculation - 4.1 Our Hindu-Arabic System and Early Positional Systems - Exercise Set 4.1 - Page 219: 70

$70,000.005$

RECALL: $10^{4} = 10,000 \\10^{-2} = \dfrac{1}{10^2} = 0.01 \\10^{-3} = \dfrac{1}{10^3} = 0.001 \\10^{-4} =\dfrac{1}{10^4} = 0.0001$ Thus, the given expression is equivalent to: $=(7 \times 10,000) + (5 \times 0.001) \\=70,000+ 0.005 \\=70,000.005$