The sum of the two sisters' ages this year is 55. My sister's age in a certain year is the same as this year's. That year, my sister was exactly twice as old as my sister. How old is my sister this year?
3. Xiao Zhang said to Xiao Wang, "I am twice as old as I was when I was your age. When you grow to my age, the sum of our ages will be 63." Find the ages of Xiao Zhang and Xiao Wang.
The best answer is 1. The age difference between Xiaoming and grandpa is the common multiple of 6, 5, 4, 3 and 2, because the minimum common multiple of 6, 5, 4, 3 and 2 is 60. So grandpa is 60 years older than Xiaoming. Grandpa is 70 years old and Xiaoming 10 years old.
2. Solution: If we directly assume that my sister is X years old this year, it is difficult to express her age, so we assume that my sister was X years old a few years ago, so my sister is 2x years old, my sister is 2x years old and my sister is 3x years old. Therefore, according to the equivalence relation of "Sisters are 55 years old this year", the equation 2x+3x=55 5x=55, so x= Sisters' age this year is 1 1×3=33 (years old).
A: My sister is 33 years old.
Let Xiao Zhang and Xiao Wang be X and Y years old respectively.
When Xiao Zhang was y years old, Xiao Wang was y-(x-y) years old (time went backwards by x-y years).
According to "my age now is twice as old as when I was your age", I know that x=2[y-(x-y)].
The above analysis shows that [x+(x-y)]+x=63.
Simplified to 4y=3x 3x-y=63.
Finally x=28 y=2 1.
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