Question

Внучке столько же месяцев, сколько дедушке лет. Дедушке с внучкой вместе 78 лет. Бабушка на три года моложе дедушки. Сколько лет бабушке?

Answer 1

Пусть Х - возраст внучки в годах
Пусть У - возраст дедушки в годах
Составим систему уравнений:
Х + У = 78
12Х = У
Подставляем У в первое уравнение
Х + 12Х = 78
13Х=78
Х=6
У = 12 * 6 = 72
возраст бабушки 72 - 3 = 69
Ответ: возраст бабушки - 69 лет.

Answer 2

78-3=75 это элементарно

Answer 3

Problem Analysis

We are given the following information: - The granddaughter is as many months old as the grandfather is years old. - The grandfather and granddaughter have been together for 78 years. - The grandmother is three years younger than the grandfather.

We need to determine the age of the grandmother.

Solution

Let's break down the problem step by step:

1. We know that the granddaughter is as many months old as the grandfather is years old. This means that if the grandfather is x years old, the granddaughter is also x months old.

2. The grandfather and granddaughter have been together for 78 years. This means that the sum of their ages is 78 years. So, if the grandfather is x years old, the granddaughter is also x months old, and their ages sum up to 78 years, we can write the equation: x + x/12 = 78.

3. The grandmother is three years younger than the grandfather. So, if the grandfather is x years old, the grandmother is (x - 3) years old.

Now, let's solve the equation to find the age of the grandfather and then calculate the age of the grandmother.

Calculation

To solve the equation x + x/12 = 78, we can multiply both sides of the equation by 12 to eliminate the fraction:

12x + x = 12 * 78 13x = 936 x = 936 / 13 x ≈ 72

So, the grandfather is approximately 72 years old.

Now, we can calculate the age of the grandmother:

Age of the grandmother = Age of the grandfather - 3 Age of the grandmother = 72 - 3 Age of the grandmother = 69

Therefore, the grandmother is 69 years old.

Answer

The grandmother is 69 years old.