It's extremely hard to estimate any kind of numbers, but I wouldn't be at all surprised if, worldwide, less than one self-proclaimed Christian in a thousand has ever heard more than about 20 verses of the Bible in his or her life. Heard. Much less read. (I wouldn't be surprised if less than one Christian in a hundred thousand has actually personally read more than about 20 verses from an actual Bible.)
Most curiously, the majority of regular churchgoers read surprisingly little of their own holy book. These have obviously heard significantly more verses (because of them being preached from the pulpit) but surprisingly many have never even opened a Bible themselves.
The obvious problem with this is, of course, that they are fed only certain selected parts of the Bible. They never get to hear or read the most problematic parts.
Not that it matters much, though. Even if they stumble upon some of the more problematic parts, they just tend to ignore them and quickly shove them aside (with at most a thought of "there's probably an explanation to this.")
Just to take one example, and not even from the Old Testament, but the new one, consider this (from 1. Corinthians 14):
Women should remain silent in the churches. They are not allowed to speak, but must be in submission, as the law says. If they want to inquire about something, they should ask their own husbands at home; for it is disgraceful for a woman to speak in the church.
This notion isn't isolated. There are other passages that affirm it, such as this one (from 1. Timothy 2):
A woman should learn in quietness and full submission. I do not permit a woman to teach or to assume authority over a man; she must be quiet. For Adam was formed first, then Eve. And Adam was not the one deceived; it was the woman who was deceived and became a sinner.
There are, actually, some denominations of Christianity that take these passages seriously and apply them in their congregations. However, quite obviously these denominations are a very, very small minority among Christianity in general (unless we count Catholicism as one that applies these verses.) In the vast majority of them these and other similar verses are happily ignored.
The vast majority of churchgoers don't even know of the existence of these verses and have never even heard of them. Those who have heard of them simply ignore them or make up hasty rationalizations. In denominations which completely ignore these verses and allow women to preach and speak in churches, obviously these particular verses are never preached to the congregation. If someone asks about them, the explanations become quite wild and varied.