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

2 & 7

step-by-step explanation:

he climbs 300 ft/hr at a constant rate. the peak is at 1,500 ft.

when going up, he reaches 600 ft in 2 hours. remember, that he is going in a constant rate. divide 600 with 300:

600/300 = 2

assuming that he takes the same route back (meaning that it's a 1500 ft route back, you can solve.

note also that you are solving when he gets back to 600 ft after he reaches the peak.

first, find the amount of hours it takes to get up the peak. divide the total amount (1500), with the ft/her (300) to get the amount of hours (x):

1500/300 = x

x = 5

it takes jamie 5 hours to get up. now, he is returning down, and reaches 600 (his current destination). remember that he climbs at a constant 300 ft/hr. divide 600 with 300:

600/300 = x

x = 2

now add the two numbers together.

x = 5 + 2 = 7

jamie takes 7 hours to go up the mountain and reach his current position when descending.

(total amount/constant rate) = (time).

remember that it is a constant rate, so in total, when he gets back down the mountain, it will take the same amount of time as when he goes up. the total amount for the round trip is: 5 + 5 = 10.

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