Question

calculați: (1.000-2-4-6-...-38-40)x10-70x80

Answer 1

$[(100 0- (2 + 4 + 6 + ... + 40)] \times 10 - 70 \times 80 \\ \\ = (1000 - 2 \times \frac{20 \times 21}{2} ) \times 10 - 5600 \\ \\ = (1000 - 420) \times 10 - 5600 \\ = 580 \times 10 - 5600 \\ = 5800 - 5600 \\ = 200$