Lusine saw birds and mice eating seeds on the ground. She calculated 12 heads and 39 legs in total. How many birds and mice are on the ground?

4.5 birds, 7.5 mice

Step-by-step explanation:

We know that birds have 2 legs and mice have 4. Furthermore, birds have 1 head as well as mice.

If b represents the amount of birds and m represents the amount of mice, because there are only birds and mice here, the total amount of birds and mice (b + m) must equal 12.

b + m = 12

Next, to find the total amount of bird legs, we must add 2 legs for each bird. Another way of putting this is to multiply 2 by the amount of birds, or b * 2. Similarly, the amount of mice legs is equal to m * 4. The total amount of legs is equal to 39, so

2b + 4m = 39

Our two equations are thus

b + m = 12

2b + 4m = 39

One way to solve this is to solve for m in the first equation and plug that into the second. We have

b + m = 12

subtract b from both sides

m = 12-b

substitute that into the second equation

2b + 4(12-b) = 39

2b + 48 - 4b = 39

-2b + 48 = 39

subtract 48 from both sides to isolate the b and its coefficient

-2b = -9

divide both sides by -2 to isolate b

b = 4.5

Therefore, there are 4.5 birds on the ground (there is somehow a half of a bird!)

Plugging that into m = 12-b, we have m = 12-4.5 = 7.5

step-by-step explan mxfcg'k; uafwgzfgjhklhgation: