David debe realizar cinco pruebas escritas, en las cuatro primeras ha obtenido 34, 65, 55 y 40 puntos, si ha de obtener una media de 50 puntos, ¿cuál debe ser su puntuación en la quinta prueba?

He must score 56 on the fifth test.

Su puntuación en la quinta prueba debe ser 56.

Step-by-step explanation:

The mean is the sum of all scores divided by the number of tests.

In this question.

5 tests.

Grades of 34, 65, 55, 40 and x. We have to find x.

The mean is 50. So

He must score 56 on the fifth test.

Su puntuación en la quinta prueba debe ser 56.

the 8 in 8,420 is in the thousands place so it's value is 8 thousand.

the 8 in 6,870 is in the hundreds place so it's value is 8 hundred.

divide 8000 by 800 to find the answer:

8000 / 800 = 10

the 8 in 8,420 is 10 times greater than the 8 in 6,870