|
|
The horizontal fraction bar was introduced by the Arabs.
Only 12 hours after an egg cell is fertilized by a sperm cell, the egg cell starts to divide. As it continues to divide, it moves along the fallopian tube toward the uterus at about 1 inch per day.
The modern decimal position system was the invention of the Hindus (around 800 AD), involving the placing of numerals to indicate their value (units, tens, hundreds, and so on).
Approximately 15–25% of recognized pregnancies end in miscarriage. However, many miscarriages often occur before a woman even knows she is pregnant.
Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.