How Old Is John Now?

  • Context: MHB 
  • Thread starter Thread starter mathdad
  • Start date Start date
  • Tags Tags
    Age
Click For Summary
SUMMARY

John is currently 8 years old. The problem states that John's father is five times older than John, and John is twice as old as his sister Alice. By setting up the equations based on their ages and solving for the variable x, it is determined that Alice is 4 years old, leading to John's age being calculated as 2 times 4, which equals 8.

PREREQUISITES
  • Basic algebraic manipulation
  • Understanding of age-related word problems
  • Ability to set up and solve equations
  • Familiarity with variables and expressions
NEXT STEPS
  • Practice solving age-related algebra problems
  • Learn about systems of equations
  • Explore word problems involving multiple variables
  • Study methods for verifying solutions in algebra
USEFUL FOR

Students learning algebra, educators teaching mathematical problem-solving, and anyone interested in enhancing their skills in solving age-related equations.

mathdad
Messages
1,280
Reaction score
0
John’s father is 5 times older than John and John is twice as old as his sister Alice. In two years time, the sum of their ages will be 58. How old is John now?

John's dad = 5(2x)

John = 2x

Alice = x

5(2x) + 2 + 2x + 2 + x + 2 = 58

10x + 3x + 6 = 58

13x + 6 = 58

Correct so far?
 
Mathematics news on Phys.org
Yes. Why didn't you solve for x and use that value to compute John's age? :)

Will you try rewriting the system so John's age is the variable?
 
John's dad = 5(2x)

John = 2x

Alice = x

5(2x) + 2 + 2x + 2 + x + 2 = 58

10x + 3x + 6 = 58

13x + 6 = 58

13x = 58 - 6

13x = 52

x = 52/13

x = 4

John = 2x

John = 2(4)

John is 8 years old.
 

Similar threads

MHB What is Peter's current age in this age problem?
  • · Replies 6 ·
Replies
6
Views
7K
MHB Age word problem: when john is 12 years old, how old is his mother?
  • · Replies 2 ·
Replies
2
Views
2K
How Do You Set Up an Equation for the Ages of John, Peter, and Alice?
  • · Replies 29 ·
Replies
29
Views
2K
How Old is John Now Based on Past and Future Age Calculations?
  • · Replies 11 ·
Replies
11
Views
2K
MHB How Old is Lee Based on the Given Mathematical Problem?
  • · Replies 4 ·
Replies
4
Views
2K
MHB How Many Dogs Did the Pet Store Sell in March?
  • · Replies 3 ·
Replies
3
Views
2K
Graduate RIP John Stachel (1928-2025)
  • · Replies 2 ·
Replies
2
Views
937
MHB What is the present age of the mother and son in this age problem?
  • · Replies 4 ·
Replies
4
Views
1K
MHB Vatha & Chris Ages: Solve to Find Out How Old They Are Now
  • · Replies 1 ·
Replies
1
Views
2K
MHB Which procedure takes the minimum time to solve modulus functions?
  • · Replies 5 ·
Replies
5
Views
1K