How long was the flood?

Gen.7:4 Says “For yet seven days, and I will cause it to rain upon the earth forty days and forty nights; and every living substance that I have made will I destroy from off the face of the earth.”  Gen.7:17 “And the flood was forty days upon the earth; and the waters increased, and bare up the ark, and it was lift up above the earth.”  So just like I learned in Sunday School the flood lasted forty days and forty nights.  The confusing thing is that Gen.7:24 says, “And the waters prevailed upon the earth an hundred and fifty days.”  So I guess the real question is which is right?  How many days did it really flood?  In Gen.8:3 it says “The bible says, “And the waters returned from off the earth continually: and after the end of the hundred and fifty days the waters were abated.”  But then goes on to say in Gen. 8:6 "And it came to pass at the end of forty days, that Noah opened the window of the ark which he had made:

8:7 And he sent forth a raven, which went forth to and fro, until the waters were dried up from off the earth.

8:8 Also he sent forth a dove from him, to see if the waters were abated from off the face of the ground;

8:9 But the dove found no rest for the sole of her foot, and she returned unto him into the ark, for the waters were on the face of the whole earth: then he put forth his hand, and took her, and pulled her in unto him into the ark.

8:10 And he stayed yet other seven days; and again he sent forth the dove out of the ark;

8:11 And the dove came in to him in the evening; and, lo, in her mouth was an olive leaf plucked off: so Noah knew that the waters were abated from off the earth.

8:12 And he stayed yet other seven days; and sent forth the dove; which returned not again unto him any more.

8:13 And it came to pass in the six hundredth and first year, in the first month, the first day of the month, the waters were dried up from off the earth: and Noah removed the covering of the ark, and looked, and, behold, the face of the ground was dry.

8:14 And in the second month, on the seven and twentieth day of the month, was the earth dried.”  Now I know why they just say forty days.  They really have no idea?