I found this easier to just explain as a factor instead of speaking of percentages. If you win, your money gets bigger by a factor of 1.8. If you lose, your mon

I found this easier to just explain as a factor instead of speaking of percentages. If you win, your money gets bigger by a factor of 1.8. If you lose, your money gets smaller by a factor of 2 or multiplied by a factor of 1/2. So you find your end value by just multiplying all these factors up. Obviously if the number of winnings and losings is the same, you’ll be multiplying by 1.8 as often as dividing by 2, so on average your money will get smaller by like 0.9 each round. Not counter-intuitive if you think in terms of factors.