math help please

[dwdreamer]

is this right? My son has to determine the scale of 2 objects.
Object A is 15cm and Object B is 4cm
Object A is given the value of 1. What is the scale model of B?

Is it 1:3.75?

TIA, math is not my thing at all!!

 

[damo]

You've got it upside down. Object A has to be bigger than Object B

I always make it into a ratio and then cross multiply.

15/4=1/x

so x=4/15 or 0.267

 

[EthansMom]

is this right? My son has to determine the scale of 2 objects.
Object A is 15cm and Object B is 4cm
Object A is given the value of 1. What is the scale model of B?

Is it 1:3.75?

TIA, math is not my thing at all!!

15 cm / 4 cm = 1 / X

X = 0.267

So 1: 0.267.

Edited to fix bad math.

 

[damo]

ignore this post. lol

 

[PollyannaMom]

My "Illustrated Dictionary of Math" (yes, I'm a geek and have one) says:

Scale - A fixed ratio that represents the relationship between a drawing (or model) and the real object. The scale is usually written as x:y, where x represents the the measurement used on the reproduction and y is the corresponding measurement on the real object.

So, I guess since object A (the bigger one) is 1, then object B (the smaller one) must be .267


P.S. - What grade homework is this??

 

[EthansMom]

15 cm / 4 cm = 1 / X

X = 0.267

So 1: 0.267.

Edited to fix bad math.

Now, I'm rethinking myself. Although, the math above is correct, on a toy model, the scale is always listed as something like 1:10... meaning 1 inch on the model is equal to 10 inches of the real object. In that case, 1 unit of measurement of object B would be equal to 3.75 units of Object A.... or 1: 3.75 as the OP surmised.

Does your son have a math book to which he can refer?

 

[damo]

Now, I'm rethinking myself. Although, the math above is correct, on a toy model, the scale is always listed as something like 1:10... meaning 1 inch on the model is equal to 10 inches of the real object. In that case, 1 unit of measurement of object B would be equal to 3.75 units of Object A.... or 1: 3.75 as the OP surmised.

Does your son have a math book to which he can refer?

But the question asks for 1 unit of measurement of object A, not object B.

If the question would have said to assign 1 unit to B, then the answer would be 1:3.75

 

[dwdreamer]

It's actually a 5th social studies question. They are studying globes and maps. The scale refers to an object on the map.I probably should have said that. His class hasn't learned ratios yet - they're doing fractions.

 

[damo]

It's actually a 5th social studies question. They are studying globes and maps. The scale refers to an object on the map.I probably should have said that. His class hasn't learned ratios yet - they're doing fractions.

Then the answer is just 4/15 units. If object A is 1 unit, object B is 4/15 of a unit.

He needs to make object A 1 unit. If it is now 15 units, it needs to be over 15 to make it 1 whole unit (15/15 = 1). That means you must also put object B over 15 as well to get 4/15.