More than _____ percent of all mammals are placental.
60
50
10
100
90
90
What is the definition of placental?
A)a mammal which gives birth to a fetus that moves into a pouch for protection and nourishment
B)a tube that connects an unborn baby to its mother for nourishment
C)having a placenta, the organ that nourishes young until birth
D)a mammal that has just one passage for elimination and egg laying
E)the gland of a mammal that produces milk for the young
C)having a placenta, the organ that nourishes young until birth
To find the answer to this question, we need to understand what placental mammals are and how they relate to the total number of mammal species. Placental mammals are a group of mammals that give birth to live young, which have developed inside the mother's uterus through a placenta. This is the most common type of mammal reproduction.
To determine the percentage of placental mammals, we need to compare the number of placental mammals to the total number of mammal species. There are approximately 5,500 known mammal species in the world.
To calculate the percentage, we divide the number of placental mammals by the total number of mammal species and multiply by 100.
So, if we assume that "x" represents the number of placental mammals:
Percentage of placental mammals = (x / 5500) * 100
Now, we can evaluate the answer choices:
- 60%: If the percentage of placental mammals is 60%, that means there are (x / 5500) * 100 = 60. Solving this equation for "x", we find x = (60 * 5500) / 100 = 3300. Therefore, 3300 placental mammals out of 5500 total mammal species would be needed for a 60% answer.
- 50%: Similarly, if the percentage of placental mammals is 50%, the equation becomes (x / 5500) * 100 = 50. Solving for "x" gives us x = (50 * 5500) / 100 = 2750. Therefore, 2750 placental mammals out of 5500 mammal species would result in a 50% answer.
- 10%: Using the same approach, if the percentage of placental mammals is 10%, the equation is (x / 5500) * 100 = 10. Solving for "x" gives us x = (10 * 5500) / 100 = 550. Therefore, 550 placental mammals out of 5500 mammal species would lead to a 10% answer.
- 100%: If the percentage of placental mammals is 100%, this means all 5500 mammal species are placental.
- 90%: Finally, if the percentage of placental mammals is 90%, the equation becomes (x / 5500) * 100 = 90. Solving for "x" gives us x = (90 * 5500) / 100 = 4950. Thus, 4950 placental mammals out of 5500 total mammal species would be required for a 90% answer.
By analyzing the given answer choices, the correct answer is 90%, as it represents the percent of all mammals that are placental.