O = 3 D
O + D = 448
substituting ... 3 D + D = 448
solve for D , then substitute back to find O
A. 149 pounds
B. 112 pounds
C. 224 pounds
D. 336 pounds
O + D = 448
substituting ... 3 D + D = 448
solve for D , then substitute back to find O
Step 2: According to the problem, the ostrich weighs 3 times as much as Mark's pet dog. So the weight of the ostrich is 3x pounds.
Step 3: The sum of the weight of the ostrich and the dog is 448 pounds. So we can write the equation: x + 3x = 448
Step 4: Simplifying the equation: 4x = 448
Step 5: Solving for x by dividing both sides of the equation by 4: x = 448 / 4
Step 6: Evaluating x: x = 112 pounds
Step 7: The weight of the ostrich is 3x = 3 * 112 = 336 pounds.
Therefore, the ostrich weighs 336 pounds.
Answer: D. 336 pounds
We know that the ostrich weighs 3 times as much as Mark's pet dog, so the weight of the ostrich is 3x pounds.
Together, the ostrich and the dog weigh 448 pounds. Therefore, we can write the equation:
3x + x = 448
Combining like terms, we get:
4x = 448
To isolate 'x', we divide both sides of the equation by 4:
x = 448/4
Simplifying, we find:
x = 112
So, Mark's pet dog weighs 112 pounds.
To find the weight of the ostrich, we substitute this value back into the equation:
3x = 3 * 112 = 336
Therefore, the ostrich weighs 336 pounds.
Hence, the correct answer is (D) 336 pounds.