The Discounted Purchases : Puzzle

Until last week, Mandy had been putting off the purchase of four major items for her home, waiting for her town's annual bargain days. Each year, the town's four main stores (including Nickels) each send out a coupon for a different percentage discount (10%, 15%, 20%, or 30%) on the purchase of a single item. Can you find the discount that Mandy received on each of her buys, and determine from which store she purchased each item?

Given:

Discounts      : 10%, 15%, 20%, 30%
Store Names : Stears, Pal-Mart, Nickels, Dullard's
Appliances    : Computer, Dishwasher, Lawnmower, VCR

Clues:

1) The percentage discount Mandy received on her new computer was twice that of the item she bought at Dullard's. 

2) The discount on the Stears purchase was ten percentage points lower than the one on the riding lawnmower. 

3) The discount on the dishwasher wasn't 15%. 

4) Pal-Mart, (which didn't issue the 30% off coupon) isn't the store at which Mandy purchased the VCR.

Click here for SOLUTION!

The Discounted Purchases Puzzle : Solution

What was the challenge?

First let's have a given data.

Given:

Discounts: 10%, 15%, 20%, 30%
Store Names: Stears, Pal-Mart, Nickels, Dullard's
Appliances: Computer, Dishwasher, Lawnmower, VCR

Clues:

1) The percentage discount Mandy received on her new computer was twice that of the item she bought at Dullard's. 

2) The discount on the Stears purchase was ten percentage points lower than the one on the riding lawnmower. 

3) The discount on the dishwasher wasn't 15%. 

4) Pal-Mart, (which didn't issue the 30% off coupon) isn't the store at which Mandy purchased the VCR. 

 STEPS : 

1] As per clue (1), Dullard's didn't sell computer to Mandy and she didn't receive 10% or 15% off on computer. Also, Dullard's didn't offer her 20% or 30%.

2] The clue (2) suggests that the lawnmower wasn't purchased at 10% or 15% discount. Also, Stears discount must be 10% or 20%. And Stear didn't sell lawnmower for sure.

3] The clue (3) suggests that dishwasher wasn't sold at 15% discount. So, it's clear that Stears must have sold dishwasher at 10%/20% discount and Dullard's must have sold VCR at 15% discount. Therefore, computer must had been bought with 30% discount.

4] And hence, lawnmower at 20%. With that, Stears must have sold dishwasher at 10% discount as per clue (3).

5] Finally, as per clue (4), Pal-Mart didn't offer 30% discount suggests that it must not have sold computer. Therefore, Nickels sold computer at 30% discount and Pal-Mart sold lawnmower at 20% discount.

CONCLUSION : 

Final summary of the all purchases in form of table looks as - 

Who knocked over the monitor?

Melissa and Jessica were working on the computer along with their friends Sandy and Nicole.  Suddenly, I heard a crash and then lots of shouts.  I rushed in to find out what was going on, finding the computer monitor on the ground, surrounded with broken glass!  Sandy and Jessica spoke almost at the same time:

Jessica saying, "It wasn't me!"

Sandy saying, "It was Nicole!"

Melissa yelled, "No, it was Sandy!"

With a pretty straight face Nicole said, "Sandy is a liar."

Only one of them was telling the truth, so who knocked over the monitor? 

Find here who did it! 

Source 
  

Person Who knocked Over Monitor!

What's the entire matter? 

If we assume Jessica speaking the truth & she is not the culprit then other 3 must be liar. The truth that comes from Nicole's statement is that Sandy is telling truth. But only 1 is speaking truth not 2 as here Sandy & Jessica.

That means Jessica is lying. Which in turn means it was she who done that damage. Now Sandy's statement can't be true as we already have got culprit Jessica. 

Similarly, Mellisa lying as she is pointing towards Sandy.Two person not telling truth at a time as per provided information.

So only left with Nicole who is telling the truth that Sandy is liar.

Hence we can conclude that, Jessica knocked over the monitor & Nicole is telling the truth.