March 3, 2015

Homework Help: math

Posted by Reiny on Wednesday, May 9, 2007 at 5:09pm.

You did not watch your units, you are mixing inches and feet

Your equation should have been
1/2 = 1/di + 1/120 (I changed 10 feet to 120 in)

solve this for di and you get 2.03 inches.

Please help me I am so confused I think I am losing my mind.

The focal length f of a camera lens is 2 inches. The lens equation is 1/f=(1/di)+(l/do), where di is the distance between the lens and the film and do is the distance between the lens and the object.

The object to be photographed is 10 ft away. How far should the lens be from the film?

my work:
1 1 1
- = - + -
f di do

1 1 1
- = - + -
2 di 10

You subtract 1/10 and get 4/10=1/di. di=2.5

but supposedly the answer is 2.03. How?

1 1 1
- = - + -
f di do

if you can't tell what i mean, this is it: 1/f=(1/di)+(1/do)

Lol, trick question! Thank you!

Answer this Question

First Name:
School Subject:

Related Questions

algebra - A rancher is putting up a rectangular electic fence to contain some ...
Math - Calculate the Volume in Cubic Feet of a section of drainage pipe that ...
Math - During scuba lessons Sue dove 30 feet. Harriet dove 120 feet, and Kathy ...
maths - height=6 feet length=5 feet breadth=4 feet volume of the container=120 ...
Algebra 1 - Please Help Me!! "Crown Molding' is a decorative strip of wood ...
math - A pound of grass seed covers 120 square feet of lawn. how many pounds are...
Math - If Sally places a rocket that is 3 feet 6 inches tall atop a launch pad ...
math - A rectangle is 7 feet longer than it is wide. If its area is 120 square ...
math - I am doing something wrong when I work this question. Can someone show me...
math - Robert planted pumpkins to sell. Their garden has 5 sides. 5 feet 8 ...