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How many pairs of natural numbers at (x, y) satisfy the inequality 3x + 5y < 20?  
  • a)
    4
  • b)
    5
  • c)
    6
  • d)
    8
Correct answer is option 'D'. Can you explain this answer?
Most Upvoted Answer
How many pairs of natural numbers at (x, y) satisfy the inequality 3x ...
The inequality 3x + 5y < 100="" can="" be="" rearranged="" as="" y="" />< (100="" -="" 3x)/5.="" />

To find the number of pairs of natural numbers (x, y) that satisfy this inequality, we can substitute different values of x and find the corresponding range of y values that satisfy the inequality.

Let's start by substituting x = 1:
y < (100="" -="" />
y < />
y < />

Since y must be a natural number, the largest value of y that satisfies the inequality is 19.

Now let's substitute x = 2:
y < (100="" -="" />
y < />
y < />

Again, the largest value of y that satisfies the inequality is 18.

We can continue this process for different values of x, but we notice that the largest value of y that satisfies the inequality decreases by 1 each time the value of x increases by 1.

Therefore, we can find the number of pairs of natural numbers (x, y) that satisfy the inequality by finding the sum of the largest value of y that satisfies the inequality for each x from 1 to infinity.

The sum of the first n natural numbers can be calculated using the formula (n(n+1))/2.

So, the number of pairs of natural numbers (x, y) that satisfy the inequality 3x + 5y < 100="" />

(19(19+1))/2 = 20*19/2 = 190.
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How many pairs of natural numbers at (x, y) satisfy the inequality 3x + 5y < 20?a)4b)5c)6d)8Correct answer is option 'D'. Can you explain this answer?
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