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## Math Brain Teaser- Erin’s Grandma

Currently, Erin’s age plus her grandma’s age equals 94. In 4 years, Erin’s grandma will be 5 times as old as Erin. How old is Erin currently?

This can be solved without any formal algebra training. Answers can be submitted below, will reveal before the week is over!

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### 15 Comments to “Math Brain Teaser- Erin’s Grandma”

1. Hendy | Profile

Grandma is 81 and Erin is 13.
81 + 4 = 85.
13 + 4 = 17.
17 * 5 = 85.

2. cheddarmelt | Profile

In four years their total age should increase by 8 (four for each), totaling 102. Divide that by six (one for Erin, five for Grandma), and you get 17. That’s Erin’s age in 4 years. So she’s 13 now. (Grandma is 81.)

3. hakoly1018 | Profile

13 years old.

4. Shawn | PUZZLE GRANDMASTER | Profile

Erin is 13

5. BlindCupid | Profile

15 2/3

6. engjs1960 | Profile

Erin is 13.

7. mimi112 | Profile

Currently Erin is 13 years old and her grandma is 81. In 4 years, Erin will be 17,and grandma 85 wich is 17*5.

8. suineg | PUZZLE MASTER | Profile

I think the answer is 12 years and 4 months
Explanation: G: Grandma age, E: Eric age
Time = 0 –> E+G = 94
Time = 4 –> E + 5E = 98 ( G = 5E 4 years later)

6E= 98 E= 16.33… years –> 16 years and 4 months, but that is in time= 4
so in Time= 0 E = 16.33- 4= 12.33–> 12 years and 4 months

9. Falwan | Profile

81;13

With equations!

E+G=94
but G+4=(E+4)X5
G+4=5E+20
G=5E+16
so E+(5E+16)=94
6E=78
E=13
Erin is 13 years old.

11. Bobo The Bear | PUZZLE MASTER | Profile

>”This can be solved without any formal algebra training.”
I’ll take a stab at the “non-algebra” solution, for a change.

The combined age now is 94. In 4 yrs, add 4 to each age, making the combined age 94+4+4=102. The ratio of these ages is 5 to 1, or five parts Grandma to one part Erin, for a combined six parts. 102 broken into six parts makes each part 17. In 4 yrs, Erin will be 17 and grandma will be 17*5=85. So now Erin is 13 and grandma is 81. And 13+81=94.

12. Hex | PUZZLE MASTER | Profile

Erin is 13 years old

13. atulatul | Profile

Erin is 17 yrs old currently

14. Sarah Al Taher | Profile

let x be the current age of Erin
y be the age of her gran…
x+y=94…(1)
5(x+4)=y+4>>> 5x+20=y+4>>>5x-y=-16…(2)
add (1) & (2) to have:
6x=78>>>x=78/6=13 >>>y=94-13=81

Erin 13
gra…81 ))