MATHEMATICS IN THE MODERN WORLD
PRACTICE PROBLEMS
TOPIC: MATHEMATICAL LANGUAGE AND SYMBOLS
A.
Choose a quantity to be represented by a variable, then write a
mathematical expression for each.
1. Karla’s age in 5 years
Let N be Karla’s age.
N + 5 will be Karla’s age in 5 years
2. A three-digit number whose hundreds digit is half the tens digit and the
tens digit is 2 more than the units digit
Let N be the units digit
Tens digit = N + 2
Hundreds digit = 1
2(N + 2)
The three-digit number is 100(𝟏
𝟐(N + 2)) + 10(N + 2) + N
3. The total interest earned after one year when P100,000 is invested, part
at 6% annual interest rate and the remaining part at 7.5% annual
interest rate
Let N be invested at 6% annual interest
100,000 – N be invested in 7.5% annual interest rate
Note: Interest = Principal amount x rate x time
Total Interest = N x 0.06 X 1 + [(100,000 – N) x 0.075 X 1]
Total Interest = 0.06N +0.075(100,000 - N) or -0.015N + 7,500
4. The distance traveled by a man driving at the rate of 60 kph
Distance = speed x time
Let N be the time
Distance = 60N
5. The fraction of work done by a man who can finish a job in 2 hours
Work = amount of work/time
Let N be the amount of work done
