Integers and Divisors | ISI-B.Stat Entrance | TOMATO 98

Try this beautiful problem from Integer based on Integers and Divisors useful for ISI B.Stat Entrance.

Integers and Divisors | ISI B.Stat Entrance | Problem-98


The number of positive integers which divide 240 (where both 1 and 240 are considered as divisors) is

  • 20
  • 18
  • 16
  • 12

Key Concepts


Integer

Divisor

Number theory

Check the Answer


Answer: 20

TOMATO, Problem 98

Challenges and Thrills in Pre College Mathematics

Try with Hints


We have to find out the number of positive integers which divide 240.so at first we have to find out the factors of 240...

\(240=2 \times 120\)

\(240=3 \times 80\)

\(240=4 \times 60\)

\(240=5 \times 48\)

\(240=6 \times 40\)

\(240=8 \times 30\)

\(240=10 \times 24\)

\(240=12 \times 20\)

\(240=15 \times 16\)

\(240=20 \times 12\)

\(240=24 \times 10\) ..............

so we notice that the divisors are repeat........

Can you now finish the problem ..........

We notice that after \(240=15 \times 16\) this stape all the factors are repeats.....so we have to calculate up to \(240=15 \times 16\) step only....

can you finish the problem........

Therefore the total number of positive integers are \(1,2,3,4,5,6,8,10,12,15,20,24,30,40,48,60,80,120,240\) i.e \(20\)

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Integer | ISI-B.stat Entrance(Objective from TOMATO) | Problem 72

Try this beautiful problem Based on Integer useful for ISI B.Stat Entrance.

Integer| ISI B.Stat Entrance | Problem 72


The number of integer (positive ,negative or zero)solutions of \(xy-6(x+y)=0\) with \(x\leq y\) is

  • 5
  • 10
  • 12
  • 9

Key Concepts


Integer

Algebra

Divisor

Check the Answer


Answer: 10

TOMATO, Problem 72

Challenges and Thrills in Pre College Mathematics

Try with Hints


Factorize the given equation

Can you now finish the problem ..........

Find the divisor

can you finish the problem........

Given equation is \(xy-6(x+y)=0\)

\(\Rightarrow xy-6x-6y=0\)

\(\Rightarrow xy-6x-6y+36=36\)

\(\Rightarrow (x-6)(y-6)=3^2 \times 2^2\)

Now the numbers of factpr of \(36=9\) i.e \(\{1,2,3,4,6,9,12,18,36\}\)

Thus we may say that 36 has 9 positive divisors, and 9 negative. and x=0 and y=0 is also a solution

the given condition \(x\leq y\) ,so there are 10 non-negetive solution

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